I ordered 2 dumbbells for hometraining and now i wonder with which weight i should start. As much as i can lift or is it better to start with light dumbbells ( although i could lift more ) ?

typically, you think of eight to ten reps in a set ... and three to four sets is a good place to start ... you want to start with a weight that you can comfortably lift to do that many reps and that many sets ...

When I got my first weight set my dad made me only put on about 50 pounds. I knew I could lift more than that because I could lift my 100 pound sister without a problem at all. My dad said I could move up in weight when I could lift that ammount 100 times. Apparently he was kidding. My arms hurt for 3 days. Don't overdo it.

i think you should take training before you start at your own. if you are not done well then your body shapes will be little damaged. so take safe training and do same at your home.