How to replace gear oil on golf 1 and where to?

Yes same oil but must be new.DO NOT USE OLD OIL

If have had this problem many times on Mk4 vw golf.
The transmission oil must be fully drained, frop the gearbox sump and replace the filter kit (widley available). Make sure everything is really clean, especially the oil pickup pipe and screen.
I generally measure the oil removed and refill the same amount. you must use the correct transmission oil....so check. I think its dextron3 or similar..but all stockists will have a listing for it.
There is no dipstick , the only way to test is using a scanner or trial and error ( i do not recommend the latter).
Chech vw forums for diagrams showing the drain plug on the sump...you never get all the oil out due to height of the neck and the fact that the torque convertor and oil coolers still have oil in them.
good luck
Roger

Since you say gear oil I assume that it is a manual transmission. Here are codes and fluid type/capacity
Transmission fluid Capacity 2.0 liters
Transmission code: DYP, ECW, EFG, ERS, FBV, FBX, FBY, EGY, EVR, EZK, FCF Type G51 SAE 75w-90 (synthetic oil)
Transmission codes: DQY, DBZ, DZQ, DZC, EGC, EGF, EKG, EMR, EMS, ENH, ENJ, EBJ, EBP, EBQ, EZH, EWW, FBW, EGR, EBN, EGT, EGX, EGU, EHC, FDS, EHA Type G50 SAE 75w-90 (synthetic oil)

my golf 4 1.8 automatic transmission gearbox change gear 1 & 2 but 3,4,5 are not changing..wht can b problem..plis help um so disperate!!!!

The 5 speed transmission has a 17mm plug that screws into to the end of the transmission, (it's to the right of the 3 inch round cap with VW on it). You can access it thru the driver side wheel well. Fill until gear oil comes out the hole.

For Manual Transmission Oil ONLY

VW pt # G052 145 A2 SAE 75 W90 Synthetic oil

You Think your mechanic did not Connect your distributor cables.

dis canekt the batrey 4 10mins and than leter it till it gows up a ger and chek the oil in it

Sounds like a stripped reverse gear. And for the second gear probally need a new gear (1st 2nd) and the syncros with a new hub. If too much metal from the gears has already made it's way around in the bearings through the transmission oil you might be looking at a new transmission. The Golf 3 generation had many problems with reverse gears. Sorry to be the one to tell you.

i have a polo 1.4 it heats up lower pipe remains cold why