Likely that you gearbox oil is water contaminated or someone as put or topped up wok mineral oil instead of the correct gear oilDoh!
The correct Audi gearbox oil (part number ending in A2) does not thicken when cold or thin when hot where as mineral oil goes like treacle when really cold making gear selection difficult until oil warms up normally after 3 to 5 miles
Suggest draining and refilling with correct oil TPS do it for £7 a litre you will need 2 litres. 1.7 is the capacity but you can’t get it all out so normal to get 1.6 back in
Unsure the fill plug comes out first
They are either 17mm hex Allen key or 12 point with a pip in the middle (latter cars use these)