What to do if you missed mincha?
It depends on the reason why you missed it. If it can be considered an accident, then you can daven maariv twice. After davenng Shemona Esrei of Maariv, daven a second Shemona Esrei as a makeup one for the mincha that you missed. After that say Aleinu
If however you’re missing it was purposeful then it cannot be made up.