In like 3 or 4 days you can learn its function and get friendly with UI. and after that you can play with it for some days. and then you can try to make or replicate some game mechanics for you game. I recommend some really good channels :
Matt Aspland, Code like me, UE4 Blueprint Tutorials, Dev Enabled, Dean Ashford
Hope it helps :)
There are not any good dedicated full video or playlist for platformer. But you can start with UE4 3d template and then try to search what you need in your game, anything you want to add/implement in your game
How to search ?
Some examples : like
'how to make movable platforms in ue4'
'how to make pickable coins in ue4'
'how to make heart health/ health bar in ue4'
'how to change/replace character in ue4'
'how to make game over screen or main menu'
And that is how you make any game
Just search what you need !
Hope it helped :)
