I,m in Berlin since July 2013, I have not taken any financial support from the government, i,m working full time since 3 years and have B2, i,m married and my son was born here in 2014
I got first one year residency permit them 3 years valid till January 2018, when can we apply for the permanent residence? and when we get it, is my son will take the German citizenship, as he is now stateless.
Many thanks in advance
you can apply for permament residency after 5 years, normally, in your case, that should be from the time you arrived in Germany (so starting in 2013) so that you would be able to apply in 2018. (-->in case you received refugee status or subsidiary protection). In some cases, howeverm the period may not take into account the time before you received your residency permit (-->you should check this point carefully with the authorities)
Until recently it was possible to apply for permanent residence Permit generally after 3 years. This has now been extended to 5 years. However, it is in exceptional cases still granted after 3 years. For this you would need - among other things - according to my information a German language skills level of C1 (but you should inquire further if your B2 may be sufficient).
Your son will become German citizen once you have been staying in Germany legally for a period of 8 consecutive years provided that you then have a permanent resideny permit.