You can search for the correct power supply on the Lenovo page: https://pcsupport.lenovo.com/de...
Just search for your model (e.g. by serial number on the sticker on the bottom of the laptop. The string after S/N) and then look in the spare parts section. Digitec probably carries the same model ;-)

Basically, if the voltage and current between the power supply and the laptop match and the plug fits, there is usually no problem. If the power of the power supply is higher, but the voltage is the same and the plug is the same, then there is no problem. The laptop will simply draw the required current. In all other cases, it could cause problems or not work at all.

Nevertheless, I would buy the power supply recommended by Lenovo or even the original one. The Lenovo support page or Digitec customer service will certainly help you...