Have you tried other versions to download and see if the same error comes up? I believe by default in the software store that Bottles comes as a flatpak, is that correct or am I misremembering?
How are you downloading your Proton updates? Bottles itself doesn't grab them unless I'm somehow missing a major update; one uses ProtonPlus or ProtonUp-Qt usually. I checked Bottles for updates just yesterday or the day before, and found none, but haven't checked the latest Proton since last weekend. I'll take a look tonight when I get home.
I can say that Proton has been downloading slower than usual lately, by a lot, so something may be up.
@applecheeks37 Bottles is only officially distributed as flatpak or source, so there shouldn't be any other version to try.
I actually went to their site to check this because I was a bit confused, they have their legacy version still available to download as a deb, but the newer version is Flatpak only (and appimage and snap "currently not available" which I swear I used it as an appimage once, but maybe my memory is going wonky).
I've been using Bottles for more than a year and a half and have helped people with a fair few problems using it. I somehow had LITERALLY NEVER found the menu for installing runners from within Bottles. Until I saw your screenshot, I was convinced there WAS no way to do that, and that you must've been confused. I apologize and stand corrected!
Bottles itself doesn't seem to have updated its runner list yet, but you can download ProtonPlus, choose Bottles in the top left corner, and it'll install for you. Just make sure you close Bottles before installing a runner this way. ProtonPlus is available in the software store.
It may have been available that way long ago or from a community build, but it's been this way for quite a while. Bottles is severely underfunded (less than 100 euros a month in donations), so a fair bit's fallen by the wayside.
I probably wouldn't worry too much about being one version or two behind on the latest GE. Unless there's some specific changes that you need for some new / difficult to run game here, then you're probably not going to notice any difference between the versions at all. Heck, sometimes there are regressions that can cause some games to stop working that were working properly.
As long as your software/game is working properly and well, I would argue it might be best to leave it and maybe check for newer versions less frequently. I often don't upgrade my proton versions unless there's something that's gone wrong and I need to see about a potential fix.
Okay so i downloaded ProtonPlus, and it does install to bottles as you said, but the thing is i can only do that to 10-13 and older versions.
When i try to install 10-15 through ProtonPlus it downloads, but nothing shows on my bottles, i can't even see this option as available.
From your screenshot, you don't see GE-Proton10-15 because you're still on the download screen, not settings for a bottle. If you want to set a new runner on an existing bottle, you need to open that bottle, click Settings, and then use the runner dropdown. You can see it on my machine here: