Getting a fixed return from an investment

Q: I give $5000 to a person in pakistan for investment. He told me that he will give me monthly $300/month on the top of that money. The condition is that the amount on top of $5000 can be $300 or more or less depending upon the business sales.

The second condition is that the owner told me that I can't give you guarantee for $5000 as incase if theres a loss then he will not be responsible for the loss.

My question is, is the $300/monthly return on the $5000  halal or haram?

Business in the musjid

Q: From what I understand, it is impermissible to do business in the Musjid. However we find that with the widespread technology around us, business methods have transformed drastically. A person could be doing banking, checking banking statements, creating, reviewing or viewing pricellists or adverts, making bookings and even doing his shopping with the use of a mobile device.

We often find people doing such form of business related work, shopping or even casually browsing through adverts which are received in the form of messages, whilst being seated within the Musjid. Is this permissible?

Pronouncing the name Muhammad correctly

Q: Different people, even Arabs, say "Muhammad"differently. I say it as "Muhammd" without the last vowel "a" and sometimes as "Muhammed" in daily life and in prayers (we need to mention the name of the Prophet (sallallahu alaihi wasallam) in tashahud and durood after tashahud. I did it in the past as this is how my non-Arabic tongue works. Does it matter for prayer?