There is very little that we don't currently understand about the laws of physics. The so-called "Standard Model" can explain almost everything. I have to admire the brilliance of the people who figured this stuff out because to understand anything more than in general terms requires very many pages of high-level mathematics.
It is not perfect. Both the Theory of Relativity and Quantum Physics are incomplete theories. They don't agree perfectly with each other and they can't explain what happened during the first nanosecond of the Big Bang. We would need a Quantum Theory of Gravity that we don't have yet. We don't know yet what Dark Matter and Dark Energy are, although we have some theories.
Some things we might never know. Subatomic particles behave like waves on a vast ocean. We may never know what the ocean is made of because it sits beneath our reality. It is likely beyond our reach.
But in terms of what makes spaceships travel the path they do, how computers compute, and why socks stick to your clothes when you take them out of the dryer, we understand all that stuff perfectly.
So besides cosmology and particle physics, what is left to discover?
1. We will never have faster than light travel. It would be a miracle and a monumental and dangerous undertaking if we could reach 10% the speed of light. Even 1% of the speed of light would be amazing.
2. Our computing technology will soon run into physical limitations where we just can't make the circuits any smaller. The next step would be light-based circuitry, but the technology is not yet even close. People make pie-in-the-sky claims about Quantum computers that are a very long way off. So it seems likely that the advancement in computer technology will slow down in about a decade. Maybe the next big breakthrough would come from software.
3. For seventy years people have been predicting that nuclear fusion power is just 30 years away. They said the same thing 30 years ago. It turns out that nuclear fusion power is very hard to do and only remotely possible on a massive scale requiring at least billions of dollars to build. We should have it by the year 2100, which is a good thing because we are going to start running out of some fossil fuels long before then. We need more nuclear fission plans, and we are predicted to get more in about a decade, but it would be difficult to build enough to power the world.
4. Renewables are going to be somewhat of a bust. They are useful on a limited scale, but they require too much land and too much raw material and resources to power the world.
5. We are seeing advances in nanomaterials that could change the world. The first graphene batteries are being developed. This could have a major impact on electric vehicles.
6. I think that we will see huge advances in biotechnology, not only in our understanding of biology and medicine but in the ability to manipulate genetic code for useful purposes. We could program microbes to make medicines and materials that we need. We might be able to cure diseases, improve our health, and increase our lifespans. Biotechnology could be the next big thing.