Buying and selling shares

Q: If we interpret various Fataawa then it seems we can purchase shares and then sell them. But some people say that if you purchase the shares speculating that they will go up and sell within few minutes or after an hour or after some days then it is gambling. They say that the sole purpose of share buying should be the partnership of the company. If we are buying shares in anticipation of getting higher price afterwards, it is haraam. According to some muftis the sole purpose of buying the shares should be the partnership in the company and not trading. My question is can I buy the shares of a permissible company and then sell it when the value goes up?

Early settlement discount

Q: We have customers who buy on credit. Is it permissible for us to tell them that we will give them a discount if they pay before the due date? For example, the customer purchases goods worth R100 000 on a three month credit basis. The customer is told, “If you pay within one month, you will receive a 10% discount”. Is this permissible?