Hi, I am an Independent Advisor.
Let me help you with this issue.
I understand that you are trying to install Euro Truck Simulator 2 and it has been going more than 10 hours.
A few factors could be causing the delay. It might be due to a slow internet connection, server issues if you're downloading it, or potential problems with the installation files. If it's taking too long, you might want to cancel the installation, check your internet connection, and try downloading the files again. Try changing your connection from WIFI to Ethernet if possible. And contact Steam Support.