Adding music (songs) into projects

What music, songs I can add? What license agreement I needed, if I want to add some songs?
And where I can find these songs? Where I can find free music?
For example can I use some songs Beatles or another group ?
If I will cut song, will be needed licence ?
Thanks for your answers)

(I am not a lawyer, so this is not legal advice. This is just my experience. You should contact a lawyer for real legal advice)

Short answer: Using ANY music without permission (a license) is copyright infringement. Even if you edit it, or only use a small piece.

You may use a song that exists already by obtaining a license. The license will give you permission to use it in your game by the holder of the rights of the music.
There are also many free music assets on the Unreal Marketplace and other places on the internet.
There are also a variety of low-cost music assets available for purchase, which are very high quality on the Unreal Marketplace.

If you need 80s synth music, I’d recommend my music asset, Synthwave 001.
If you need techno music, check out Techno001

You can also find a lot of game composers who work for free (so they can build a nice resume, finding paid work is extremely hard for a composer), then you can ask them to write music similar to the copyrighted music you want. AFAIK, music licensing is very expensive.