206 auto transmission problem

I have 2006 Peugeot 206 auto I can’t drive in auto but when I go for manual selection first and second gear isn’t working but the third and fourth gears work perfectly I drove on highway on 80speed in fourth gear no problems it is showing the code (slipping clutch/brake) anyone can help me with this problem please
Mechanic said have to change the whole gear box

 

My Mums Peugeot 206 the auto gear box completely failed the first time it was driven for an hour in the first week she bought it. Peugeot offered to replace the the auto transmission. The car has been seldom driven more than an hour at a time with only 40000 klms on the clock The next time it was driven for 3 hours it has completely failed again this time out of warranty. Quoted $3300 to fix. Is it possible to change the auto to a manual gear box? Or just bite the bullet and get it fixed or get a second hand replacement. My 90 year old sharp as a tack Mother and previous owner of a 504, 205, with the 205 still going reliably, now thinks PEUGEOT must be an acronym for (Piece'f Expensive Useless Garbage Expect Ongoing Trouble)