How do I play with my friends on epic games?

[jieesos]

I don't wanna make an account on epic because I don't want to lose my progress on steam

[Major Raquel ~ヾ(・ω・)]

You don't share progress files between Steam and Epic.
About inviting your friend, this says it in the FAQ

I'm an Epic player. How do I invite my friends?
You can invite them by clicking on them in the in-game friends list, then pressing the invite button. To invite a friend that plays on Steam, invite their linked Epic account.
You can only Join from elsewhere on the Main Menu, if your friend is in a match or lobbyOne of you needs to be a match or create your own squad before you can invite your friend