Broken office chair

I echo what other said. Get yourself a new one.

Argos and hunt office both have a wide range of quality style and price.
 
you might find a full replacement base if you look around.

Like this one, but they don't deliver to us in the EU
https://www.amazon.co.uk/Hartleys-Black-Office-Castor-Wheels/dp/B017MENWCO/ref=asc_df_B017MENWCO/?tag=googshopuk-21&linkCode=df0&hvadid=435914815898&hvpos=&hvnetw=g&hvrand=10002554090642164460&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007850&hvtargid=pla-680501631312&psc=1&tag=&ref=&adgrpid=102798546698&hvpone=&hvptwo=&hvadid=435914815898&hvpos=&hvnetw=g&hvrand=10002554090642164460&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007850&hvtargid=pla-680501631312