Problems fased at interview when we don't know english are:
 we can't speak any thing in frenght of any one
the person who is listining to that he can't respond to that
he will be tennxed for that
he may not answer anything and he may loses that job

If we don't know english, then :
1) we can't understand what question have been asked.
2) we even can't reply.
3) we may lose our confidence if in front anyone speaks english.
4) from begining, we may get scared and take tension about what will happen in interview.
5) risk of not getting job