Losing power when vacuuming

[lange]

Bought a house with a pool in May.
the equipment must be 25 year-old. It's an old jacuzzi FM

when I vacuum, there must be some air going into the pump. Because all of a sudden, the vacuum stops working... almost no water comes out of the jet... and there's less water in the pump... it fills with air.

Then What I have to do is lift up the vacuum... when it's not sucking solidly on the bottom of the pool, it's less likely to happen.
Or I can disconnect the vacuum for a minute until everything starts working again and then I can continue vacuuming for sometime (May be 30 seconds or 3-4 minutes)

Can the problem be the old pump. I changed the rubber rim thing where I unscrew to take the basket out.


Also... one of my jets and the drain at the bottom of the pool are not working... is there many reasons for that or are they just clogged???
Not working means nothing at all.


By the way, I have an inground pool