Family Reunion Visa

Hello,

I had applied for a family reunion visa to join my spouse in germany. I have got a visa for 3 months starting 1st august till end of october. Is this normal that we get a temporary visa initially and then we have to go to the german city and register at the local office and get a longer visa? As a non-eu citizen, how do we take care of health insurance in germany? I already found a job in germany and they are asking for some documents including tax statement, social security card, membership of health insurance, police certificate? I guess this all will be obtained during the registration process.. how much time it takes for registration at the local office in germany, if anyone has an idea?

Regards,
Worrie