Hey Jhonny! great to see you've started a sketchbook here!
I really like your life paintings ,and the robot shading is very nice :p
For the speedpaints, don't be afraid to experiment with a lower horizon (view closer to the ground), It seems like most of them are aerial views.
Putting down a perspective grid would help getting a better sense op depth.
And remember, less is more! Dont get lost too much in detail and focus on the general composition and values.
its good you're doing lots of speedpaints..its a good way to practice and improve.
But anyways, keep updating this sketchbook , and..keep drawing! (:
Some great stuff! But I would highly suggest you look at the basics, because it seems like you are trying to run before you walk. Try loomis and vlippu stuff--you can find them free online, and they'll help you lots. Keep drawing buddy! Excited to see ya improve.