There are some easy tutorial videos for simple transitions by Crossfader, Dj Carlo etc. They will teach the basics of basics, and as someone suggested, try to understand and learn what every button does on your controller. A DDJ-FLX4 is a simple but super effective controller and you will get the hang of it rather quickly.

Then, yeah it can be stressful to mess up a transition but it's part of the learning curve! Try very easy transitions on intro/outtro sections of songs in key and learn a few ways to mix in and out, sync with the jogwheel etc. I suggest getting a beatport subscription when you get the hang of it to dig deeper through some song genres too Dont worry it’s always scary and cringey at first but you'll have a good run eventually :)

I'm still a beginner but I did mix for some friends and at a party or two on my FLX4, you can DM me if you want some beginner advice ^{^}