Will deleting the app lead to loss of all data?

Account data is always stored on the servers.

However in order to get access to your account after reinstall you need to either link it to Google / Apple / Facebook account or write down your PlayerID which you will find on the settings screen. (Not your 9-digit ally code but a longer alphanumeric string)

That said, level 36 is trivial to get back to. You have barely scratched the surface of the game.