Can we add an ssd

Looks like that is an NVMe M.2 2280 on the right lower part of the picture and right next to it (on the left) is an empty slot for a 2nd drive of the same type:

https://guide-images.cdn.ifixit.com/igi/...

Have to look up prices more locally to where you are.

Its a fairly straightforward operation, so yes, taking due care its easy.

When installed, if you run Windows then open up Disk Management and make sure it shows up, format it/assign drive letter if needed/as you like, then you'll have the extra space available in Explorer.

All the best, welcome to ifixit!