Guild Wars 2

After finishing my first Fractal my personal lvl increased from 1 to 2. So – in order to get to lvl 50 I should play Fractals at least 48 more times? That means – I can not directly increase from lvl 2 to lvl 5, for example?

Correct, you can’t go straight from level 2 to level 5.

You can play at a higher level than you’re currently entitled to get rewards from. The difficulty of the fractal will be that of the level you play at, but your rewards will be earned as if you were at your current reward level, and your fractal level will increase by one afterwards.