Lithops usually germinate pretty quickly, how long ago did you plant and where are you, what are your temperatures and growing conditions like?

I've never germinated Lithops but I have germinated plenty of other things. Why are you concerned about the condensation in the bag? It won't stop anything from germinating as far as I know. However, too much sun can make the temperature in a bag or sealed container too high, basically cooking the seeds.

Open the bag little to allow air circulation. Have the pot standing in a saucer with a little water to keep the pot moist. Lithops are very prone to damping off which is what your conditions are encouraging with the closed bag. Once germinated, I remove any enclosure around the pot and mist daily.

I planted them 2 days ago now and the pots are biodegradable so they are turning very squishy and drenched. Yesterday I think it was about 20 degrees centigrade but now it is very cloudy and colcold so they are still inside but now for some reason the big pot has water which is brown.

I've never grown Lithops from seed, but have grown lots of other stuff - cactus, Hoodia, Edithcolea, Pachypodium, Adenium, and others. I always enclose mine in bags or clear plastic boxes at least until they germinate. In the case of cactus a lot longer. I don't worry about the condensation; you don't want them to dry out at that stage.

Don't put pots enclosed in bags/boxes in direct sun or they'll cook. Indirect light, filtered sun, or under lights is good.

Edited to say... if Lithops are very prone to damping off (as s g says) give them a bit of air circulation. You just want to make sure to keep the potting medium damp until they germinate.