As I’m half Arab/half European, my Arabian family tried to talk my native language. One of them wanted to say “I love you” which is in Dutch “Ik hou van je”.
He ended up saying; “ik geil van je” which translates along the likes of “I get horny of you”.
Also in Spanish, you want to say “Tengo calor” = “I have heat” instead of “Estoy caliente” = “I am hot”, because the latter is used to mean “I am horny”.
My Spanish teacher also told us of a time he had taken a class to a Spanish speaking country and a student accidentally broke a glass while in a restaurant. The student wanted to exclaim “I am very embarrassed!”, but used a false cognate and instead exclaimed “Estoy muy embarazada!” = “I am very pregnant!”
Also in Spanish, you want to say “Tengo calor” = “I have heat” instead of “Estoy caliente” = “I am hot”, because the latter is used to mean “I am horny”.
I've heard someone translate "dat is geweldig" not with the correct "that is amazing" but "that is like violence", which shows amazing skill in Dutch grammar, but a tiny lack in knowing words.
For those not fluent:
"Geweldig" means "Amazing", but "geweld" means "violence". Meanwhile, most words that end in "-ig" are nouns used as adjectives, like "fun" -> "funny".
Similar thing happened to me with the Spanish speaking coworkers Lol. I wanted to ask a new guy his name (but trying not to say "¿como te llamas?" Which means "how are you called?) and accidentally asked for his number.