kouty 0 Junior Poster in Training

Hello, there.
Before a lot of years, my main work in computer was made with Ubuntu because I have a computer without an official bought Windows version and I was afraid from a not legal work. When I bought this PC, in spite of that i made a double entry with a choice to enter with Ubuntu or Windows. When I upgraded the version of Ubuntu, suddenly everything started not working. And since the number one option was to start with Ubuntu, it was freezing and no one was able to help me, i made the computer turning on with Windows only. But Ubuntu is steel here.
I wand to clean from the PC the Linux and try afterward to install Mint.
How can I do this if possible. If not I want to free space in the PC and cancel any Linux. Because it takes a lot of the computer storage capacity.