You have establish the reason why the piping can’t deliever adequate amounts of water. Eiher:
1. Waterworks operating pressure. Call your local waterwork and ask what they are delivering in your residental area. This should be between 300 and 600 kPa. If that is in order, you can rule it out. Then your problem should be either of the following.
2. The pipe leading into the house. Either clogged or to small diameter. Inadequate capasity.
3. The pipes delivering inside your house. (Same as in 2)Inadequate capasity.
4. The faucets. Pressure lost due to dirt inside or as with self-regulating temperature faucets causing much resistance.
You could increase the capasity of the main intake pipe by installing a pre-pressurized tank. And you can increase the pressure delivered from the waterwork by means of a pump. And there exists systems combining the two, increasing the capasity. Installing this could be one solution. Another solution could be to replace old and clogged pipes with new and wider diameter. You could also replace faucets and shower gear into something causing less pressure loss.