Native Brazilian Portuguese speakers: Which English sounds do you struggle with the most?

Hello! I’m a non-native speaker of English and a university student doing research for an assignment on the English sounds that speakers of other languages struggle with. The language I’ve been assigned is Brazilian Portuguese.

If you’re a native Brazilian Portuguese speaker, or a teacher who has taught Brazilian Portuguese-speaking learners, I’d love to hear about your experience:
Which English sounds do you find particularly difficult to pronounce?
Are there any English sounds that you consistently have to practise or think about?
Would you be willing to send me a short audio clip showcasing a sound you find difficult in a word/phrase? 

I’m doing this research as part of my university coursework at Universidad Tecnológica Nacional (UTN), Argentina. The recordings would only be used for this university assignment and for analysing English pronunciation difficulties among Brazilian Portuguese speakers. 

If you’re comfortable contributing, I’d really appreciate a short audio clip of a word or phrase containing an English sound that you personally find difficult. I’m particularly interested in examples where you feel that the difficulty results in a noticeable mispronunciation or pronunciation issue, even if the pronunciation is otherwise understandable and does not need to conform to a specific accent such as RP or Standard American. In other words, I’m interested in sounds that you consider difficult and/or that may still be perceived as a pronunciation mistake, rather than simply differences between accents. 

Thank you very much for your help!