How can I expand my memory from the notebook so do I have to add an external memory card for PC games?

So I have 1256 Gb of memory and it is full except for C: 32 Gb and D: 10 Gb

You could install a bigger hard drive. Where 2Tb SSD are not cheap or just a 2.5 inch HDD.

Or get an external hard drive, where you can outsource a lot.

Another hard drive does not fit, you can only replace one. But I advise you to get an external one and put your photos and videos and documents on it. And then install the new games on an internal hard drive, otherwise you have eternal loading times

Videos take up a lot of space (example). Get an external hard drive with USB connection

Formatting on the PC and files and videos etc. Simply slide onto the external hard drive. Of course, also possible with the memory card.