Outlander 2010 20% more incorrect speed
 

Hi all!
I have an old Mitsubishi Outlander 2010 V6 LS and I see that compared to the GPS it shows almost 20% more on the speedometer than the GPS.
If I am travelling with 100km / hour, the car shows 120. Do you know what might be the problem or how to solve this?
The car has standard wheels and I am not aware of any repairing done before as I bought it used 2 years ago and was like this.

thank you in advance, Dritan