Hi Maria Camila,
there are a lot of good suggestions here already.
I think it really depends on what you want to do with your English. If you think that your native accent, keeps you from being understood by English speakers, then you could work a little on your intonation or pronunciation.
But that is not the case, don't worry too much about it if people understand what you are saying !
There are so many English accents out there !
I am saying this, because we, as language learners, tend to be very hard on ourselves.
You could discuss this with your tutor or language exchange partner and see what they think.
If the situation is really as bad as you say, you could check for exercises on intonation. Shadowing is very helpful too !
When you shadow, you take a recording and the transcript and you try to read out loud at the same time as the recording.
It is very hard at first, but after 6 or 7 times, you get the pace and you start to get better. This really helps with intonation.
Songs too are a very good tool.
There are quite a few good free resources out there for accent training, you just have to google them.
Best of luck !
I guess for some people it's just hard to get rid of their accent. But try watching English movies and imitating their accent, talking to yourself in that way everyday, that's one way of getting rid of your accent and getting the accent that you want.
Btw if you sound like Sofia Vergara, that ain't so bad! ;)
Well the most important thing is to be understood. I live in London, which is very cosmopolitan, there are all sorts of accents. If your accent gets in the way of comprehension, then you need to work on it, but even in the UK there are different dialects. I once took a university girlfriend to the NE of England where I was born, and she couldn't understand a word - yet polls show that people in the UK like that accent and regard is as being 'genuine'. If it bothers you that much, then mimic some native speakers; learn some songs; try shadowing.