Rectifying one's mistake

Q: I'm a Muslim and I was currently sitting with a group of non Muslim people. They asked me if drinking is allowed is Islam and I said it is Haram, however they asked me if it is ok to take drugs like weed and cocaine and I accidentally said it is ok to take drugs realizing later that I made a mistake and gave wrong advice as you are not allowed to take anything that can harm the body in Islam.

Cancelling a partnership

Q: 20 years ago, Mr. Zaid invested Rs. 50 lakh in a business. All the items were purchased from his money and it was decided that he would get 25% of the profit. The other partner agreed on working in the store. Mr. Zaid also kept on visiting the store until he got sick 5 years back. Now if he wants to end the business with mutual agreement, will he get Rs. 50 lakh? Or since the value of the money has increased alot, he will get extra benefit?

Paying off a loan after one's creditor passes away

Q: I was given money for five years investment by one of my friends but there was no written agreement. It was only verbally discussed. Now my friend passed away and he is unmarried. His family are all well off and they don't even know about this matter. I can't pay before five years but I can pay this amount in monthly installments. Can you guide me on what should I do?

Sisters claiming a share in a business

Q: Whilst my father in law was alive he had a property and business which he gave to his two sons legally. Then both brothers decided to spilt, so again legally my husband gave his brother his share and paid him out.

My father in law at that time told my husband that when he gathers enough money, he will give his seven daughters 3000 each. My father in law passed away last year. Now when giving them 3 000 the sisters are saying that they are entitled to a share in the business and property because their dad built it. Islamically are they?

Is it a requirement to go to a musjid to accept Islam?

Q: I recently was asked by a non Muslim if I can tell him the shahada to make him become Muslim because he wanted to become Muslim. So I told him the shahada in Arabic and also in English and explained what is Islam and what you should believe in to be a Muslim. He did it and he believed on what we all Muslims believe so he became Muslim.

After some time this guy asked me that someone told him that the shahada you believe and the things you believe in that the other guy told you. With that you can’t become Muslim because everything he told you is true but you must go to a masjid and repeat it with the masjid Imam so he can repeat with you then you will become Muslim. The other guy took him to a masjid and the imam repeated the same things.

My question is that is this guy became Muslim the first time I repeat the shahada with him or no he became Muslim when he met the masjid imam which one is truth  Can someone regular not an imam make someone become Muslim ? Or no only imam can make someone Muslim ? Am I sinful because I told him shahada first time and he believed it?