How could I make this look better overall ?

Hey everyone I'm building a gallery with some other specific tools made on an api in aspnet.

I just finished designing the barebone home page and I'd like some help to improve all of that. I'm mainly a backend dev without any exp in frontend dev so if you can provide me some cool ressources I'd appreciate.

I would like to make make the images fit together despite their aspect ratio but I've legit no idea how to do that. I know that there is a coming css feature that will allow us to do that but it's still in development at the moment so I can't use it yet.

Also the right side of the navbar is the user modale button (the profile picture is just blank for that user)

Thank you for you time :)