Welcome. Are you studying English formally at all? Do you take classes? Are you having private tuition? Are you studying independently at home?
There are many resources on the internet. Of course, some are better than others. This forum is a great place to ask specific questions about the English language. You can also simply read threads posted by other members - reading the answers to other people's questions can be very helpful and sometimes you do not need to ask your own question!
If you want to improve your written, more formal English, then grammar exercises and formal learning are very helpful.
If you want to improve your comprehension and your spoken English, the best way is to find a native speaker and meet for conversation classes. If you are in a major city in Spain, I'm sure you will be able to find some native speakers by looking online. There may even be an intercambio (language exchange) held at a local venue (usually a bar!) You can also watch TV and listen to the radio in English. Do not worry if you do not understand every word - just become familiar with the rhythm and cadence of the language.
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