Rebuild roof antenna !!!!

Hello Omi municipality!!! Maybe you can help me further??? I would like to exchange the original antenna (standart AM/FM-GSM) for an AM/FM-GPS antenna. Today I ran and dismantled the panel and looked for the strippings as they are actually usual, but I found only from the antenna two lines which are equipped with screw couplings (FME) and the power connection is completely missing. On the attached photo my antenna is only that I have no GSM connection because i The problem now is that I can’t get the two strippers out far enough and then they disappear in the sheet metal. Do you know where the lead continues ????? If I make it tomorrow I will take photos of the original antenna. I am grateful for every answer!!!!! Vehicle Omega B 2.2 Facelift Built 2001