starting minecraft problem

sorry for my spelling i am from slovakia and young when i dowloanded modpack and i start him it didnt work then i stop minecarft another day i found when i start minecraft i see on version there is modpack shown but the modpack only show when i start them up from twitch but i see there is option to switch to version 1.16.2 then i click it and when i wanted to start minecraft i says user stil conected and when i started the game but the servers, texture packs are gone and when i stop minecarft i tried another modpack but it still shown me there is the modpack what i didnt start and there is not modpack what i wanted i dont know what to do completly delet minecraft and dowloand it back ? and when i tired to start optifine it dont work