I’m not very clear about what your problem is, do you mean:
1/You created a Google Sheet in your Google account.
2/You created an app and link to that spreadsheet?
3/You’re asking if you make changes in that spreadsheet will it sync to Glide? If you did step 2 then the answer is yes.
4/You’re asking if you can change an app’s source sheet? Yes you can do that.