zhroguexe I would check your collision masks, maybe your sprites have too many collision points.
800 x 300 is probably why your experience fps drops , remove it & try playing the game on mobile .
Since you mentioned "Total sprites that are making the background: 9 (which are repeated)" - If the fps still drops try making sure that sprites are being properly managed when off-screen i.e if you have to delete them then do that or if they "loop" (like in flappy birds &/or doodle jump) make sure its looping properly.
[Looping is always better for performance oppose to creating/destroying sprites that are repeatedly used in the layout]
I'm sure you already know this but make sure your game's resolution is 16:9 ( For best support across multiple screen size ) -
- You may have to research your hardware's resolution specs
Suggestion for Debugging:
Try stripping down your game.
Remove everything & disable events that don't have to do with the core functionality of the player
Also : "Every Tick" events consume a lot of memory thus could have a negative impact on your game's performance
Also : Try disabling collision for the background sprites unless you explicitly need collision detection for them