I spent yesterday in Aberystwyth with two Czech friends and we talked in a mixture of Czech, Welsh and English, with occasional bits of other languages thrown in for good measure. When they were speaking Czech to each other I found that I could understand or guess enough to get a basic idea of what they were talking about, and in some instances I could understand quite a bit more.
While I have been learning Czech on and off (more off than on in fact) for quite a few years, I rarely get the chance to listen to Czech conversations, apart from on online radio, and I was pleased to recognise quite a few of the words and phrases my friends were using. I couldn’t contribute much to the Czech parts of the conversation myself, but that will come with practise.
Quite a lot of the vocabulary and structures they were using have appeared in my Czech courses or in Czech texts I’ve read, so I was at least somewhat familiar with them already. Hearing these things used in context really helped to fix them in my mind. It also helped that I could ask about anything I didn’t understand – this is not possible when I’m listening to online radio or watching films or TV programmes.
This kind of immersion can happen anywhere you can find some native speakers of a language you’re learning (L2) who are willing to help you. Being in a country where your L2 is spoken is an even better form of immersion, but might not be possible for everyone.