wrong. They grow towards the light.

So tell me, how do they know, wich way to grow, when they are still underneath earth surface?

Actually, plants do display gravitational tropism in addition to that withe regards to light. Plants grown in the dark still grow upwards, for the short time they survive.

Only small amounts of plants grow towards light.

Phototropism isn't the only tropism that exists. Some grow towards light, away from light and also grow towards as well as away from gravity (Geotropism). There is also thermotropism, thigmotropism.

wrong. They do both.

they do none, plants aren't real

They do all, they're 6th dimensional

Technically that's right. Plants even react to mechanical stimulus (like climbing plants that react to mechanical resistance by changing the direction in which they grow).
Plants are pretty fucking awesome, if you think of it this way...