Just once / Always never goes away?

[Android Central Question]

I keep using Gumtree to find and share something with my partner. Every time it gives me the option to use an app I do not use to share things. I slide over to Whatsapp and select always. The next time I send something it goes back to the app I never use for anything (but can't delete) and doesn't even show whatsapp on the front page. I have already tried to reset all app preferences and it has made no difference.

Can I get it to stop asking me if I want just once or always every-single time?

Can I get Gumtree to sort set on my preferred apps?

Thanks