It is true that German cockroaches climbs only at night?

Yes, it's true. But if they are in the house, you'll see them.

But, they love the heat, so they live only in warm areas. Believe that if the temperature drops lower than -5 s - cockroaches die.

So, if you can, wait until the winter, open all doors and windows in the house one day and stay at the neighbors :) During this time, all the pests will disappear

Like all bugs they like dark places, but it is not uncommon to see them once in a while in the daylight. You need to get a professional exterminator to completely get rid of them, but if you want to try you can bug bomb the house, and treat around the entire foundation inside and out with insect killer.

I suggest a professional exterminator though.

they mainly come out at night...they will venture out during the daytime when they want