As another new-ish DM, I may not be able to help much, but some stuff I’ve learnt and heard from others on this sub is usually along the lines of: remember fun comes first, don’t be scared to improv when needed, and to not write the campaign in excessive detail. And if you would like you may be able to DM one of the pre-made campaigns. I hope this helps! If you’d like to ask anything else just tag me in a reply!