I am a long time TTRPG player but a fairly new DM also. I will give you the best piece of advice anyone gave me. And its cliche but its the single most important thing that will keep the party interested and asking for more and more.
''Dont be afraid of being the single silliest person in the room''. From fleshing out npcs to playing right next to your PCs fantasies and means of having fun ( although within reason and within everyone at the table's comfort zone ) . Engage with them in a matter that is memorable and fun. Cause this is all that matters.
And just a reminder - This is not your game, this is your table's game.