Poor water pressure is questioned when it seems only one person can shower at a time and if someone flushes a toilet the person in the shower gets scalded. A booster pump is sometimes is suggested. If the pressure is near 50 psi, it’s volume that’s the issue. If there is enough water volume available, you should be able to operate all your faucets and still have adequate pressure at two points of use.
I had a problem with water sharing, not low water pressure. Whenever a second faucet was turned on the first one lost one-half of its pressure. The problem was with the water service; not enough water could get from the water main to the house. That house had a 70-year-old lead line from the water main to the house. The main could deliver 50 psi but only had enough diameter to deliver say 3 gallons per minute. A shower needs about 2.5 gpm. Using the shower alone is fine, but if a toilet is flushed now each appliance will only get 1.5 gpm each, scalding the shower.
However, your problem could be in the internal water lines because you do have a mixture of copper and galvanized, which is not good. Electrolysis happens wherever dissimilar pipes are connected, often restricting water flow. Also the old galvanized lines are probably clogged. I would recommend converting the rest of the house to copper plumbing before considering a booster pump. Then if water sharing is still a problem, you could consider investigating the water main from the house to the city. The bad news here is you are responsible for that line. Check with city records and see if you can find the date and type of line installed. This information will help in your decision. Skip the booster pump; I do not like to use a pump to do something that should work fine.