Can I do graduation again after post graduation ??

Yes, you can take up your graduation course through distance education even if you have acquired the Masters degree.
However, ensure that the university so chosen is the recognised one and has the UGC affiliation. Latest marks obtained in the last graduation would be treated as your final marking for your graduation course.
In no way, it is objectionable, even though you are having a Master's degree.
Your Master's degree will remain valid despite your second attempt in the graduation.

You can do graduation in another group even after completing your Post graduation. You can do the course as a Private student. Otherwise, you can do your graduation in distance education mode. Based on your interest you can select BA or B.Com if you are an HEC student in Intermediate. If you are MP/BiP student in intermediate you can go for B.Sc. B.Sc should be studied in distance mode only. BA.B.Com can be done as a private student also. You have to select an institution which is having UGC recognition. Otherwise, there will not be any used and your degree will not have the recognition.

Welcome as your interest is teaching profession. Only really interested persons can bright in teaching profession. Your post graduation will help you to proceed for B.Ed course (if your interest is as teacher in schools) and for M.Phil for your interest is college lecturer. There are many universities offering B.Ed or M.Phil courses and you can opt the subject of your graduation or post graduation.

Normally when you are qualified as post graduate that is taken as the final document to review and treat you for the eligible criteria. I do not know for what reason you want to study the graduation again. Low marks should not irk you to compel for doing the graduation again. Instead concentrate on how to go ahead using your post graduation studies and get benefited through it. What I feel that one should not be backward looking in life and go forward with forward looking attitude and what ever happened in past should not hinder you to consider better options waiting for you as of now.

Yes, you may do the graduation again from any recognised university. I can understand that you may be facing the problems in various entrances where they ask for minimum 50-55% score.

But I am not sure if your Master degree will be considered in that case because one cannot pursue the masters after the graduation course.

If you are already a post graduate but you had poor marks in your graduation then you can again opt for doing graduation from a recognised and approved institution for improving your score in graduation. There is no rule that stops you to go like that. In fact if you are not successful in it you can again go for graduation that is even multiple attempts are allowed till your date eligibility is there. The thing is by doing that you are spending two valuable years of your life during which you could have risen in your career much. So, choice is yours whether to take advantage of good marks in your post graduation for making some career where graduation marks do not matter or go back to graduation improvement exam. Remember time is also an important entity and loss of time is also to be considered seriously in such situations.