This is an idiom hard to teach someone something new a. go out on a limb
b. play by ear
c. teach a new dog new trick

"Teaching an old dog new tricks"

Explanation:

"Go out on a limb" means that you do something risky for someone else. (Going on a narrow limb on a tree).

"Play by ear" means you improvise as you go. (Playing an instrument after hearing a song immediately).

"Teaching an old dog new tricks" means sometimes it's hard to teach someone something new if they become set in stone about something. (After a dog has passed a certain age it may be harder to teach it tricks).

≧◡≦

Mocha here! If this answer helped you, please consider giving it brainliest because I would appreciate it greatly. Have a wonderful day!