If you are learning several languages at the same time, you must have experienced the confusing feeling of mixing up words from different languages in a sentence. This happens mainly when those languages stems from the same basis, Latin related languages for example (Spanish, Italian, French, Portuguese).
Even when your interlocutor easily understands you, it can be quite embarassing when you are being assessed, in an academic lecture for example.

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Here are some tips, from personal experience, in order to avoid common mistakes:

1) As much as possible, avoid learning languages that are very closely related (Spanish- Portuguese)
I found it very difficult to distinguish between those, since they are indeed very close. Hence, I couldn't build an oral sentence in Portuguese, without including in it some "hispanismos" (says my Portuguese teacher). In the beginning, I perceived it as a challenge to be able to talk in both of them in a pure way, but I confess that I finally gave up with Portuguese and decided to focus on Spanish. Indeed, from my experience, it is more profitable to learn thoroughly one language, than to multiply two superficial experiences.

2) Understand the working of each language (English- Latin related languages)
Some languages have their own specificities and it is helpful to memorize them : for example, "function" in English will be translated into "função" in Portuguese and "función" into Spanish. You will notice that the stem remains unchanged : what changes is the termination. Keep in mind that the English "tion" is the equivalent of the Portuguese "ção" and the Spanish "ción". That tip can be useful when switching from one language to another, however it is highly variable between some languages.

3) Listen a lot (French,Italian,Spanish,Portuguese)
A good way to differentiate between languages is the pronunciation : listen to videos and podcasts so that you can see the differences between Italian "chiamare" and Portuguese "chamar" !

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