Gear slips into neutral

New post to my questionable transmission / steering parts question.

This is my issue it actually got into 3rd gear once not in the video but after that it just kept sliding out into neutral.
Very inexperienced think it’s not getting enough pressure to make the switch/ stay in gear. You can hear it switch when it at a lower power but once I try to give it enough gas to accelerate in that gear it slips into neutral.

Steering parts needed??