Video player that has a cross dissolve option when changing the clip so I need a Video Player, that can change Videoclips, using cross dissolve or overlay. It will be used by a DJ and he would like to be able to switch the Videos live by himself but not having any hard cut.
Do you have any ideas?

Thanks
The functionality you seek is standard for a item called a Video Switcher.  Video switchers can be found as both standalone units (low-end to 4K broadcast) and as software (also low-end to high-end).  In the latter case, the computer running the switcher needs video I/O functionality, which typically requires adding one or more special cards (video I/O is different than a graphics card driving a computer monitor).