Congratulations on including the relevant information — so many learners fail to do so. In a way, you’ve answered your own question. You write “I understand English very well, but when it comes to speaking, I sometimes forget the words.” You need to practice the skill that’s challenging you. Of course translation is *not* the only method, but if you choose to use it, I’m afraid you’re going to need to translate from Portuguese into English. You should keep it within your ability, for example, just use ANKI flashcards to practice individual words — that way, you won’t have to worry about grammar while working on vocabulary (work on grammar separately). At the same time, get lots of exposure to spoken English so you develop the ability to understand in real time as you gain passive knowledge of vocabulary and sentence structures. Happy learning!
Bem vindo a italki, e boa sorte na aprendizagem !