Grape Vines will take years to grow. You probably need to wait a long time bro. The soil has to Keep moisture for a sweet grape. For the first year, You do need to apply compost by mixing with your soil or feeding fertilize around the seed you grow. please keep a good humidity for the grape seedling. For the second year, You do better apply NPK(10:10:10). A handful NPK spread around your grapevine.
ENJOY YOUR GARDEN!
Grape is vine, not a tree. You can grow it over the pergola (but I have to chop it down because it is damaging the pergola. It is my fault that we didn't keep on pruning it to keep it in check)