If you are confident with you grammar and vocabulary, find someone to speak to, and you will start thinking in that language. This may also happen when reading. Eventually you wont feel the need to translate everything you read to Polish or English, and you will find yourself thinking in Spanish.

I agree with Poli.

I will add that learning "disconnected" pieces of language makes it harder to actually understand how a language works. It's far better to learn bits of language in context. That's why conversational methods are so popular, and also the reason why most language courses start by "finding oneself" in the foreign language.
For example, let's suppose this is your very first lesson and you're taught the first sentence to introduce yourself:

- Me llamo Dolores.
It doesn't matter what the exact translation is. You understand this person's name is Dolores.

- ¿Cómo te llamas?
The question is addressed to you. In context, you know that told you her name, so you're supposed to respond with yours. And you already know what sentence will be needed to say it.

Now you know "me llamo" for "me" and "te llamas" for "you". The next exercises will include more people and you didn't need a translation to start comfortably conjugating the verb "llamarse" and its pronouns.

Taking simple situations and associate sentences with them works far better for me than taking a sentence and try to understand it without a meaningful context. After I master the sentence in that situation, I usually try to apply this kind of sentence to other contexts (which usually involve making a lot of mistakes and learning new things). At first, writing sentences is all I can do. Then I can write paragraphs.
I'm not very fond of Skype exchanges and the like so my speaking capabilities are rather limited. Yet, when I can have someone to help me, I set the level that suits me, and they react with corrections and hints for improvement (there's no reason why this wouldn't work in Skype anyway).

I think it's just a matter of finding what works better for you to start producing sentences in the foreign language and do it. Also, we have to internalize that we'll make mistakes, we'll find difficult issues and we won't be perfect as we start. Go ahead using what you know and don't be afraid of corrections, as they're the basis for improvement. Practice makes perfect. ;)

I see. Thank you very much for your advice, guys. :)

Tell me, what do you think about usig L-R method?

You can use these books (21 books in Spanish) for L-R method learning:
And free audiobooks from here: