Could I get some help regarding game modes and changing levels

Hi…

I am currently making a small game which has a different amount of small levels.

I have coded all the important mechanics of my game and making a few small levels.
I have coded how the scoring takes place in my custom gamemode.

I am not sure how to progress after that.

I want a selection screen where there are a number of levels and the player selects which one to play and that levels loads along with the character.

So should I create a different game-mode for the level selection screen? And when the player selects which level change game mode, spawn character and load a level?

And the different levels I have, all have different conditions to finish the level. So should all conditions of different levels present in only one gamemode?