Advice for positions with new partner!

I started seeing someone new and they are … rather well endowed. The length is not currently my issue but rather the girth 😅 lube and foreplay definitely help but I’m still struggling but I was wondering if people had advice for specific positions that may help? Or things they do to help relax their muscles beforehand? 😅

Note: I do not have vaginismus because I have no problem with tampons, fingers etc / have not had problem with more average sized/smaller partners in the past