Can we submit part of our assignment after deadline? I have a deadline for handing in my assignments. One of them is tricky and I need to think more. I coded it but I am not 100 % sure that is right. Can I think more about it after deadline of submitting the assignment are passed I give it to my professor?


What will be his reaction? 
Will he give me the mark of that question?


PS: I submitted my assignments I also did that part, now I want to think more about that part. You know, that part was difficult.
There's nothing stopping you from thinking about it after the deadline, but if you want any corrections to be graded, you need to tell the professor before the deadline. It's possible he'll give you an extension, especially if you have good reasons (e.g. personal issues). 

Handing in assignments after the deadline, without warning, is likely to lead to it simply not being graded. The professor must be fair to other students who might not have had the extra time, and besides, if he accepted your submission everyone else might start doing the same and the deadline might as well not be a deadline.