virtualbox.org

I installed virtualbox (.run file) on Ubuntu Mate 19.10, and when I start my virtual machine and then try to move it whole window it's impossible to do it, and the window can only be resized using the right bottom corner but it causes flickering and slowness even if guest addons are installed, in Ubuntu 18.04 LTS the resize and moving was possible and smooth.

See https://www.virtualbox.org/wiki/Linux_Downloads. 19.10 is not supported yet. I'm sure the developers are working on it.

Either try the "All Distributions" link on the above page, or the test builds. If neither work, you'll have to wait until 19.10 is supported.