hello, I would like to know what you think of my technique and where can I improve?

hello

I am learning myself, but I will try to help.
In some of your drawings they seem to neen more values, more darks and lights for wxample the one with the boat. looks to me a couple more layers would improve it alot.

In the portraits, try to get rid of the lines as much as possible, use more shading to define the arms in your first portrait, and also the hair in your last one.
This is if you are looking for realinsm of course.
the nº 4 portrait seems very good to me, I only think those lips are to dark comparing to the rest of the drawing, they would need some more hight lights.

I would advice you to see thte lessons on drawing hair and mouths, they are very good and will help you improve on these small details;)

You are on the right way, just need to refine one or two things;

hope this helps you out

Very great start to drawing. I really enjoy your style. I would have to agree with Kaly about the tonal variances, this will come with more drawing, and drawing some more Also agree, more layers, take one of them and lay down a couple more layers over it and you'll be amazed!