Help with 1st person movement/turning in a Legend of Grimrock style game

Hi! I am a total novice so please bear with me. I am trying to make the character move in the style of The Legend of Grimrock or like in the old dungeon crawlers. I can make the character move and rotate at 90 degrees, but it kind of snaps from one position to the final one. I wanted to smoothen the transition, so i searched for an answer and in all the threads i found with this type of question the answers were timelines +/or lerp. But no matter how hard i tried I could not make it work. My character either would just move just a little, or it would keep orientation, and move the whole body in a circle around a specific point. I wanted the oposite: keep the location and smoothly turn 90 degrees to the right or left.
Oh, and also, it would be great if somebody showed me how i can keep rotating 90 degrees if the button is still pressed, with small stops between every 90 degrees. I tried loops, but no luck. The version i’m using is 4.12.5.

Also, please keep in mind that i am a novice. Thank you.