ecdsa – How to get the coordinates of a compressed G-spot?

I really can not deal with this ECDSA thing … So far, I know that this is used to validate transactions by signing a signature on the signature of the transaction. I've come to the mathematical part of ECDSA, but I just can not find sources that are newb-friendly or explain everything in detail. I checked out the datasheet for the secp256k1 and all recommended values ​​for the different variables. In the datasheet there is the G point, which is in both compressed and uncompressed form, but I do not understand how to find the X and Y values, the actual coordinates, and the location of the base point.

Does anyone have a SUPER well-explained guide or anything on how the math behind it works? It's for a really important order on Thursday.

Thank you in advance.