Hi Aleksander Żukowski,
I am Dave, I will help you with this.
Windows has very limited partitioning capability, if it meets an unmovable file on the drive it will refuse to perform the partitioning task and so it is best to use a 3rd party partitioning tool to perform that action.
Rest assured if you use a reputable 3rd party tool like the free version of AOMEI Partition Assistant, that wil cause no difficulty or corruption on your drive, they are very reliable.