Hi Floria,
Firstly i would like to say the game is very beautiful and it is clearly a labor of love that has had alot of time spent on it.
the comments i list below are me being as critical as possible to give you the best feedback i can to make your game the best it can be... you should be very proud of what you have accomplished thus far and i don't wish to offend.
I have a pretty modern Huawei ELE - L09 (aka P30) which is a reasonably modern phone and i think perhaps some peoples perceptions of the game being laggy are down to:
a. the low framerate of some of the animated assets (the water in particular on the main screen is probably the main culprit). the animated bees, birds and lillys all move at a good frame rate so i can tell the app is not lagging but the water i think is just right at the wrong speed, perhaps getting a smoother animation for this or bluring between frames might help. another option might be to slow it down quite abit more to 1/2 or 1/4 speed... sounds silly but i think then it will be obviously an intentional choice to have the frame rate slower then rest of the game.
b. your approach to horizontal scrolling hasn't quite hit the mark... if you swipe from complete left to complete right it swipes as i would expect but if i start 1/3rd of the way in... or drag without letting go it dosen't move. I think perhaps you are waiting for the person to let go of there swipe before figuring out what they want to do and this is part of the laggy feeling people were getting. I think you need to perhaps change it so that once you've confirmed its nolonger a tap (afew frames) then immediatly start moving the screen with the players gestures.
Other items
1: Once i made it to the seed selection screen the the tutorial hand seemed to indicate it would like me to click and drag my chosen seed to the pot, but it was more of a tap to bring up the seed and then a tap and drag it once it has popped up. perhaps you could change the tutorial so it first asks you to tap to open the packet and then once the player as preformed that action move to the part where it drags?. It might also be good to allow people to drag directly from when the seed is in the down position?. I think this problem was perhaps exasperated by the fact that the "locked" seeds were interspersed with the usable seeds in that pretty pattern... I originally assumed that the different coloured evelopes were just that way for stylistic reasons and not because some of the seeds were currently unavailable... perhaps leaving slots empty with a button to goto the store or a lock symbol with some information on how/when these would be unlocked would be more obvious?
2: When i was stuck on the item above... (i thought perhaps it was an error as you discribed you were having with huawei phones) i restarted the app, this i believe advanced the tutorial to the next step which ment even though i had yet to complete that action i was nolonger being told that was something i had to do ( i mean... i knew but tutorials are supposed to be there to help the lowest common denominator get aquainted with the game... i know my nana would love this game once she knew how to operate it but getting her to that point takes a lot of hand holding, and if at any point its not working she would get frustrated and give up)
3: when i got to the florest studio part and was reading the card i could still interact with the vase / objects in behind the card while reading it.
4: I think your choice to make all the "critical ui buttons" stylistically the same as the rest of the game is aesthetically really pleasing and i think it dose add something to the sort of exporation kind of feel but it sucks for readability... the tiny shell for the sound menu took forever too find. I think things like the buttons to scroll left and right on the main screen, The compass for the minimap, the sound menu, the help article and the exit buttons to most of the menus need to be differentiated from the background perhaps use less detail and put a nice thick outline around them and perhaps shove them all in a menu bar along the top or bottom so they are availible at all times and easy to find. you actually already have some great help resources like the help article thing and the mini map but i think they need to be in for face, easier to find.
5. you could improve the readability of the pots, If someone were to leave and come back to the game on another day it is not immediately clear at what stage your pot is at (undug,dug,planted,watered). The flag saying the name of the plant i think should come up when it has been planted rather then after watering... i also think if someone trys to do any of the actions out of order some kind of pop up should remind them what step they need to complete... like if you goto the seed area before you've dug the pot it will remind you that you need to dig a hole first... in some cases you actually have this but you've placed the message at the bottom of the screen where my fat fingers just cover it up (also thin scrawling stoneish coloured text over cobble stones is not easily legible). Could also perhaps implement a small glow around the correct tool if someone is on that screen but hasn't done anything for a few seconds it will give them a hint as to what to do next.
6. The compass in the top right dosen't stick to the screen but instead lags behind it slightly when you are scrolling the main screen left toright, I assume it is setting its x&y to some view port variables perhaps of an object that comes after it in the order of operations?. it might be good to change the compasses position in the same script that you use to scroll the screen so that the happen at the same time as the screen moves... same for the scroll buttons at the bottom.
7. The pearl mini game should perhaps come up with a tutorial that pops up the first time you discover it explaining the rules
hope that all makes sense, if you require further elaboration on any of my thoughts please let me know.
) and having a cheer to the (statistically) 3.5k people that really enjoyed your game and had a good time doing....whatever you do to keep plants alive (not my forte).