I've been in sales 15 years now. Check out these resources and they will give you a GREAT foundation:

Read the challenger sale: https://www.amazon.com/Challenger-Sale-Control-Customer-Conv...

and read SPIN selling: https://www.amazon.com/SPIN-Selling-Neil-Rackham/dp/00705111...

Listen to the advanced selling podcast: https://advancedsellingpodcast.com/

Cheers