Typical mistakes when you meet someone you know
1. How are you? – Thanks, fine – No, it should be ‘Fine, thanks’.
2. How are things? – It’s good – No, ‘I’m good’.
3. What’s up? – out of context – said when you see something is wrong and not as a greeting.
Typical pronunciation mistakes
1. I went to mountain – I went to the mountains.
2. I have an event – like Japan, Brazil – stress the second syllable not the first.
3. Comfortable, vegetable, police – all need to be shortened.
Typical mistakes in questions
1. Why you did this? – Why did you do this?
2. What for you need that? Spilt the first two words and add an auxiliary verb – What do you need this for.
3.’How long are you in Poland?' – here we need the present perfect ‘How long have you been in Poland?
English (UK) 
Polski