My PhD thesis is in French, can I take parts from it, just translate them to English (without any paraphrasing) and use them in my next paper? would this cause any plagiarism issues?
If it's properly attributed, then it's no plagiarism and with a PhD thesis there should also be no copyright issues (You should check whatever you signed to publish that though, just to be on the safe side).
There are a lot of papers that effectively start with something like "This article consists of material that first appeared in the authors PhD thesis [..]" and "This article is an English language translation of [...]". Assuming that you intend to publish parts of the thesis as a paper, yours would just be a combination of the two.
A slightly different thing would be to only reuse some paragraphs or smaller sections, e.g. a literature review or descriptions of an experiment. Again if attributed, this is no plagiarism, but generally this is a bit frowned upon. Personally, I'd see it as a sign that you are either too lazy to adapt the section to the specific context of the new paper or that the new context is identical to the old one, which then begs the question why there is a second paper in the first place. Even there, there are however times where doing so is reasonable and a translation of material otherwise unavailable to non French-speakers could be one of them.
Edit: Also please don't just "translate without any paraphrasing". There are always some formulations and sentence structures that work in one language and not the other. Those should be adapted.