Vrb phrs. To make a mess of something, to make a mistake. E.g."I don't think the job's mine, I made a complete bollocks of my interview."
MAKE A (COMPLETE/TOTAL) BOLLOCKS OF SOMETHING
Meaning of MAKE A (COMPLETE/TOTAL) BOLLOCKS OF SOMETHING in English
Slang English vocab. Английский сленговый словарь. 2012