VW Golf V (2005, 1.6L, 102HP) - Engine Temperature Stuck at 75-80°C: Thermostat Issues?

Hello.
I have a VW Golf V from 2005, petrol, 1.6, 102HP engine. I have had an engine temperature problem for some time. Until some time everything was fine, even 90 degrees. One day it warmed up to 75-80 degrees Celsius and since then this temperature has been maintained with normal driving. However, when I stand in a traffic jam, the temperature then reaches these 90 degrees.
I searched a bit on the internet what could be the reason. Many people point to a faulty thermostat.
So gentlemen, what do you think could be causing this situation? Is it actually most likely a thermostat? If anyone can advise where I can find exactly this thermostat, I would very much be asking for help. I searched and looked, but I did not find it, and I think I would be able to replace it myself thanks in advance!

The reason the thermostat does not close you have a large coolant circulation all the time.
https://www.google.pl/search?client=opera&q=V...8&oe=UTF-8#q=vw+golf+5+1,6+wymiana+termostatu

Maybe check the coolant level at the beginning and bleed the cooling system after turning on the heating to max. If this does not help, connect the car to the computer and check if the liquid temperature in the engine is close to the indications on the clocks, because the 2-pin temperature sensor may distort the indications. If you decide to replace the thermostat, check the review materials on the forum beforehand.

Replacing the thermostat helped. Thank you.