2013 GLK 350 4matic, Roof Leaking near the rearview and pillars and Im worried possibly the firewall may have water because some came from near my stearing wheel but may be build up from the roof. I have drained the sun roof drains and there was a bug stuck in there so I thought I was good. It rained again and it was still leaking and again near the rearview mirror and pillars so I'm thinking the seal on the sunroof is bad and this might seem dumb but if the sun roof is closed then how would water even get to the drains, it would have to be a sunroof seal correct? I trested the drains with the sunroof open with a bottle of water and took the pillars off and headliner down, it just went out this little side hole which I have read on here somewhere MB designed that way so it collects in a little pan and drips down the pillar, why have the holes at all? Lol that makes no sense to me.

Also theres a small leak in my windshield but closer to the passenger side pillar and both the driver side floor and passenger side floor are wet. There also seemed to be a little water on the back passenger side floor and it also sounds like water is sloshing around somewhere which is also why I fear the firewall. I am going to try the sunroof drains again but does anyone know how I can seal the windsheild without replacing the whole thing or If I missed any other possible spots water could be leaking besides where Ive stated that would cause water to drip from rearview?

If anyone could please give me some pointers or answers I'd really be grateful. I just bought this about a month and a half ago and obviously the used car salesman didnt disclose this leak to me butbwhen I bought it, it was raining but wasnt leaking at all which i find very odd. I really can't afford to have it get ruined or cost me anymore money and desperatley need to figure out cheapest solution possible unless Its absolutley necessary to replace the windsheild and/or sunroof seal. Thankyou