How to deal with a research internship manager with very bad English? I am a computer science student in a research internship. My superior is technically a professor, but I work with a PhD student. My goal is to help them run experiments to finish their thesis. They are not my manager, but I am still supposed to do what they want, and I could not find a better term, hence the title.

This PhD student's English is very bad, to the point that I sometimes cannot make sense of their messages and instructions, though I'm close to bilingual (neither of us is a native English speaker). It is slightly better in person, but I don't have many occasions to talk to them since they are working remotely for the time being.

Constantly asking them to repeat can get tiring for both of us, and I don't want to start a conflict. Pointing out that their English is simply unreadable is likely to come across as insulting too. Furthermore, I know that their experiments have a tight deadline, and I would like to help them meet it, but this constant miscommunication prevents me from working efficiently.

If it matters, the professor who oversees us agrees that it is difficult to communicate with this student. I worry that coming to the professor to complain about it could be seen as agressive by the student, and as an attempt to justify delays by the professor.

How can I deal with these unreadable messages and very unclear instructions?
It is the professor's responsibility to make sure that the instructions you are given are clear and understandable, and besides it's in their interest to make sure that you are able to do your job. So you should definitely talk to the professor about this issue, preferably giving a few examples and explaining clearly and objectively why it's a problem for your work. As you are clearly aware, it's not a matter of criticizing the person, it's matter of finding a way to work efficiently.

On a more diplomatic note, I assume that this PhD student has to write papers and will certainly have to write their PhD in English, right? So it's also crucial for them to improve their English level. Maybe you could suggest helping them at the same time: when their instructions or explanations are unclear, you would propose a better phrasing or point out why something is a mistake. The idea is to avoid that the PhD student feels bad about the whole thing, and this way they can appreciate that you're also doing some effort to make things work.