iPhone 11 apps dark background.

I’m finding in particular instagram so far, when I do a post, it is a dark background and I dont know why....I've checked all sorts asked questions and checked on You tube with no help. I’ve even deleted the app, reinstalled it, the LAST version came up and that was a white background but then it changed back.

Any help would be appreciated as I like Instagram but its very annoying to try and write on a dark background and it’s putting me off using the app for that reason.

Thanks.