suggestions for the developer to help make anytune app more user friendly

hi applevis, has anyone tried this app? Anytune - Slow down music without changing pitch by Anytune Inc.
https://appsto.re/sg/8GFWy.i
it is quite accessible but can be better. for example if i want to add markers or loop certain parts of the track, it is not so easy to move to the exact spot. i like to write to the developer but not exactly sure how to bring it across and what can he do to help. i hope someone can try it out and give some suggestions. thanks.