aniakrysia

I'll second that recommendation!  His Affinity Photo: Solid Foundations course, available via Udemy, definitely lives up to its title.  James Ritson's YouTube videos are also excellent, but without the course structure.

Another recommendation for Simon Foster (aka Drippy Cat). I recall commenting in a review of Simon's Udemy courses that he not only shows you what to do but also explains why to do things in a particular way. I think you'll find it a great way to understand better and save yourself considerable time and frustration.
 
MarkW has provided the links to some free intros Simon did that'll give you a sampling of how his lessons are taught. The Udemy courses have some free preview sections and the rest is paid (very reasonably priced). Also, Simon is very helpful and responsive if you need help. Highly recommended.  Full disclosure: I have no connection with Simon other than being a satisfied customer.

My response to this is personal. For most images, jpegs are probably more easily edited than raws. Where the raw images score is if there is some over or under exposure  or some similar problem . In such cases, it is easier to recover a useable image from a raw than from a jpeg. This is based on my experience. Probably 90%  of images I take using raw+jpeg, I find the raw confers no advantage. But it is there if I need it! I should add that I am not, in any way, a professional photographer.

Hello aniakrysia and welcome to the Affinity forums:)
Have a look at the following links to some YouTube lessons from forum member Drippy Cat that he has made for beginners.
I think you will find them most useful in getting orientated and started with Affinity Photo.
Have fun!
Affinity Photo Tutorial for Beginners - 101 - don't panic!:
Affinity Photo Tutorial for Beginners - 102 - What is a Layer?:
Affinity Photo Beginners 103 - 5 Essential Photo Editing Steps:
 

I used PhotoShop for many years before using masks, layers or brushes. I did use many plug-ins for post-processing along with adjustmens not on layers. Even today, using Affinity, I do most post-processing in a similar way. I would suggest that you stick with what works for you and learn other techniques gradually.
EDIT: I should add that this was  mainly in the pre-digital age, and I was mainly editing scanned slides.