https://www.bing.com/videos/search?q...FE4E&FORM=VIRE Look at about 2:45

https://www.bing.com/videos/search?q...4B&FORM=VRDGAR

As Goenrdoug noted, you have a threadless adjustable stem (maybe more accurately a threadless headset and an adjustable stem.)

Anyway ... Seriously, go to YouTube and browse videos under the appropriate headings. You will see pretty quickly if the stuff they are working on is similar to what you have.

The fact that two of us were able to find this stuff so quickly tells me that you can find it too .... maybe not so quickly as it would take you longer to figure out if they were working on a bike like yours ....

I think Park Tools has a good series of videos on useful stuff .... but .... as I say all too often to people, "Google it."

One big annoyance I have with people nowadays is that everyone has a smartphone connected to just about all the information in the world ... and nobody uses it. back in the day people had to go to libraries and look through hundreds of magazine articles to find anything even vaguely related, or read half-a-dozen books looking for some info which ended up not being there. (Plus, we had to walk uphill to school both ways in the snow ... even in the summer.)

If you don't know the right name for a particular part (like "adjustable threadless stem") we can tell you, and from there you can find more info than you need.

Because I don't have an identical bike, I cannot give you perfect advice for how to fix or adjust every bit and piece, but between the folks here and the Internet we can find enough for you to assemble the answers you need.