Tips for a bj when my mouth doesnt open super wide

I recently got a boyfriend who as of a month ago was my first kiss. Eventually Id like to please him but only with oral to start as Im more confortable with that first

But Im really worried about how wide my mouth can open. To be completely honest, I dont know what a punishment looks like or how big it is, but even so Im worried I won't be good at it because of how wide my mouth opens

My gag reflex shouldn't be a problem, but on top of maybe not being able to open wide enough causing me to accidently use teeth, I dont really know how Im supposed to do it... like at all. I really need any sort of advice

Any tips would be helpful. I feel like this is weighing on me because I dont have anything else to offer my bf to satisfy him. He's the best so Id really like to keep him /: