Best way to teach a god to fetch / return and drop?

Hi all, on walks we find our dog will fetch the ball and ether drop it in front of us or at least come so close and rop the ball yet in doors anything he has toy wise if we go near him he gets protective over it and wont drop it, leave it or play in general.

Any ideas on the best way to teach this? obviously it would be more fun for him to play than just be chased / left alone when hes being silly about it.

ive tried having treats but then once he knows theirs treats involved he drops the ball full stop and isnt interested so then i cant teach him.

Thanks

Scott