Hi I'm currently riding the trek fx 7.2 series,
7.2 FX | Trek Bikes

Need some help here for upgrading to improve the performance

which are the parts I should change first to improve its performance ?

tyres ? What brand and type would suggest?

gear set? 105 series? Deore? Or others. Does it helps a lot? What would you suggest

what other parts should be considered?

is er4 grips good or what other grips is recommended and where can I get them. Current grips ain't that comfortable.

Can I check the brakes to disc brakes? Current is calliper

Lastly, does it affects the warranty after I change its parts?

all suggestions are welcome !