Volkswagen Golf 1993 Several problems

Hello, I am new in the forum, I registered because I bought a 1993 Volkswagen Golf, let's start because I bought it very cheap since it is automatic and the box is only in reverse (something that I am seeing if I fix or sell it), for the moment that does not worry me but I have other problems

the first is that the temperature sensor stops working, it can be 30 minutes on and the needle stays in 0, how can I fix that? Any cable will have been released?

The second problem is that the brake practically does not stop, fill the brake fluid and the same thing happens, it presses and the pedal goes to the bottom without stop and sounds like "SSSSSSHHHHH" as if throwing air ..

the other is the Sunroof, who filters water, is that change of tires only ???

At the moment I have it as a project to fix it little by little, I do not know what they will recommend, if it will be convenient to fix it or simply sell it x what they give me for

greetings!

Hello Sebamal, the reverse, I would start looking at the speed selector, check the hydraulic fluid and the change filter to see if it stays in a little problem (also if there is no dirt in any valve of the box ..)
The temperature sensor (it carries 2 in the water box) you can see if it is not disconnected or damaged, the one that corresponds to the frame is 2 poles (for the ECU it takes another of 4. Another issue is that the wiring that goes to the box or the box itself is not well.
The solar roof if the tires are bad to change them, but adjust the hinges to make it tight (if you are not broken).
According to what he breaks in the change (if the engine does not have any greater), you must value it yourself if there are spare parts that are not very expensive for your area, try to fix it and you can always get it more benefit than if you sell it as it goes. Greetings!!!

And I forget about the brake, you may have the servofreno drilled (from there the air noise when stepping on), also check the empty tube where the anti -background valve goes and this, in addition to purging the brake fluid of the 4 jaws.

Thank you Ismael53, with regard to the sensors, do you know that the other day I clean a little where the engine goes and all that, may that have happened there, could you tell me more or less where I should look that everything is fine? (Attached photo)

Greetings!