Is this your first 'move' to an SSD?
If so, even a 'budget' SSD will be a substantial improvement over a traditional HDD, and the cheapest will be fine.
Looking that website over, you can have a 240GB Transcend SSD for 72EUR, which is a more appropriate size.
https://www.varle.lt/kietieji-diskai/transcend-ssd220s-ssd-240gb-intern-64cm-25inch-sata--2469559.html
An SSD should never be close to full, and a 120GB will fill up fast.