It’s unavoidable. If you learn a new language, you will, sooner or later, put your foot in your mouth. My students have come out with a few good ‘uns over the years, but I had one recently which topped all others.
It was a pre intermediate class, and involved a conversation about what sort of animal you would like to be. Assuming, of course, that you had to be an animal; no choice in the matter, etc. I chose a sloth, because it’s very lazy – I like lazy.
Twenty minutes later, and one of my female students was merrily chatting away, saying how she wanted to spend the weekend doing nothing.
This amused the chap next to her endlessly. “Ha ha ha! You’re a slut!”
It took me a few moments to realise that he wasn’t commenting on her sexual habits, but was using previously learned animal vocab. We worked on his use of the ‘th’ sound. It’s not as commonly used in Spanish and tends to be pronounced more softly. Too softly, on this occasion…!