hi,
Duplicate title alias entry detected. A number has been appended to the existing title alias to avoid URL conflicts. Alternatively, you can simply edit the title alias to your liking, as long as it doesn't conflict with another item's title alias.

I get this waring when i insert the same string at the same level in a different category. Can i solve this issue?

Hello,

A duplicate alias will create potential issues. You can alter the alias manually so you won't have duplicate aliases.