Hi,
I'm new here and I just bought my first bike. I had to assemble it myself and I run into a problem with my front wheel. I think my axle on the front wheel is to short and it doesn't go all the way throught the dropout. Here is the picture of it. Please help, can I extend it or do I have to buy a new wheel?

Its a quick-release wheel, missing it's skewer. Easiest is to get a skewer and learn how to use it. Swapping to a nutted axle is possible, but a bigger hassle. Locking skewers are available if you're worried about theft.

No, I have the skewer, but i didn't show it on this picture. I'm worried about the axle that looks like it's too short. There is a gap between the end of the axle and the edge of the dropout.

It's normal for a quick release wheel to have that gap.

thank you

"There is a gap between the end of the axle and the edge of the dropout."

This is as it should be. The skewer needs to clamp on the dropouts NOT the ends of the axle so the axle is necessarily shorter.

And be sure to learn to use the quick release lever. Look up instructions. VERY CRITICAL you do it properly. Having your front wheel fall of while going 30 mph down hill would be a bad day.

Here's the first decent video I found with a quick search