A post in a forum is not going to be enough. You may need to get
a tutor who specializes in accent reduction. In the meantime,
imitate native English speakers as much as possible, even if it seems
to you that you are making fun of their pronunciation!
You will almost certainly have to drill on the differences between "b"
and "v" - a distinction not made in Spanish. And another problem
is probably words that begin with "sp", "st", and "sc". Try to
glide into them from the preceding word to avoid having them sound like
"esp", "est" and "esc".
You might try to find some audio practice materials on the
internet. It depends how much you can afford to spend on this
project.
The longer you wait before getting help on correcting your
pronunciation, the more difficult it may be to break any habits you may
have already established, so it's a good sign that you are now looking
for help on this.
I wish you the best of luck!
CJ