I got a 4 English language gcse. retake?

Yes honestly I think you should retake it. Currently a 4 is a C but that is uncertain for the future and employers and universities are likely to say that they will only accept 5 as a C in future years (because the grade boundaries are currently subject to change). This is particularly true for the more competitive universities, e.g. Russel Groups. I am in Year 13 and have received offers from 5 Russel Group unis with A*’s in both English Language and English Literature GCSE’s but a B in maths GCSE. I would have taken my maths exams again if I had got a C because many Russel Groups prefer candidates with higher GCSE grades as they use GCSE grades as an indication of work ethic.
(however A-Level grades and work experience / extra curricular things are more important when it comes to applying for uni!)

Yes honestly I think you should retake it. Currently a 4 is a C but that is uncertain for the future and employers and universities are likely to say that they will only accept 5 as a C in future years (because the grade boundaries are currently subject to change). This is particularly true for the more competitive universities, e.g. Russel Groups. I am in Year 13 and have received offers from 5 Russel Group unis with A*’s in both English Language and English Literature GCSE’s but a B in maths GCSE. I would have taken my maths exams again if I had got a C because many Russel Groups prefer candidates with higher GCSE grades as they use GCSE grades as an indication of work ethic.
(however A-Level grades and work experience / extra curricular things are more important when it comes to applying for uni!)

What course did you apply for

This is a bit late but I would highly suggest you retake your GCSE English Language, at least. I'm not sure what the current situation is for you. but I am looking at retaking it too (I got a C) even though I am aiming to finish my first year at Uni and apply to a 'better' one, and I have to pay £811 to retake it since I didn't get a D or below. Most top tier Universities look for a B and above in English. You might be lucky and find some that don't (I don't think Durham does?) but the majority - if not all - Russell Group Uni's require a B in both English Language and Maths.

Most only ask for a 4 or c for gcse. But it depends on the course. Only really really good unis like top 5 ask for a b

It depends.
Are top 20 unis alright?
If Not then I recommend retaking

Yes top 20 is fine

I think retaking is the safe choice, but I don't think a lot of Uni's require Engineering candidates to have a B in English?

Correct

What are your uni choices?

Loughborough

Then you're fine

What about Durham and Warwick

Should I retake my gcse if I want to get into Russel group. Has anyone got in Russel group uni with a C in English. I want to do engineering at uni btw

What engineering course?

Yes