Shortening one's salaah if one is afraid that someone might come in the room

Q: Is it sinful to shorten a prayer if you’re either afraid if you don’t, then someone might come in the room and mistakenly walk in front of you or because you don’t want them to hear you (I deal with anxiety)?

A few weeks ago, I shortened a prayer once by leaving some sunnahs due to the first scenario. Do I have to repeat it?

Paying a fixed rate for electricity

Q: Is it permissible to enter into a fixed plan with ones energy supplier? By fixed plan I mean entering into a contract to pay a fixed price per kWh for any gas/electricity used during the coming year. The alternative is to remain on a variable plan, which means that the price of the gas/electricity fluctuates depending on market prices.