Game says levels completed when they aren’t

The game is saying that I have completed many levels but I have not done so. I even went way back and started completing any level that only had one star above it again just to make sure that I had done it, as many levels in a row just had one star, which was not realistic as you can get different numbers of stars depending on your point score, which obviously varies. Unfortunately this did not work, and all it does is move me on another lot of levels that I haven’t actually completed, and then says on the leaderboard that (for example) I have completed 15 levels. I’m literally going forward only to go backwards all the time and it’s very confusing. This all started when I found that the game said that I had completed every single level possible, which I had not done! And then it gave me hundred and hundreds of boosters which I had not earned! It’s all very strange and basically the only way I can prove to myself I’ve done a level is by going back and repeating any with only one star otherwise the game just says I’ve done them. I’ve tried deleting the app and reinstalling it, and I have received emails from help centre staff. They just said they had me on a certain level and had never heard of this before.

Any help would be much appreciated