I think, lots of people these days have an inflated understanding of time, because of the time travel trope in pop culture, as well as videos and simulations with time sliders being readily available.

Without getting into Einstein's theories for a moment, time is something we measure, we never modify time in reality.

In particular, we measure the progression of causality. Say, you kick a ball, then the atoms in your foot push the atoms in the ball, the whole ball rapidly accelerates and then takes 0.6 seconds to hit a wall.

You can't just set the whole process to -1x speed and expect it to happen in reverse. That breaks causality. The ball would need to fly towards your foot without anything giving it a push.
With our time sliders, this may seem like a small difference, but it's just completely different from anything we've ever observed in the universe.

Now, about Einstein's theories, all of the above is still true. However, Einstein has discovered that travelling through time is possible, but only going forward in time, at a different speed than everything else.

Basically, causality has a speed limit, which happens to be the speed of light. (We believe photons to be massless, so with our usual acceleration formula, any acceleration would make them go at literally infinite speed. They don't, which is why a speed limit for causality is assumed.)

Gravity and your own speed can influence this speed of causality for you, meaning at a lower speed of causality, things happen less quickly for you and you'd age more slowly.
So, theoretically¹, you can get into an extremely fast spaceship, spend 5 years-as-perceived-by-you in there and then land on an Earth that's in the year 3000.
That is a one-way trip, though, because going backwards is not a thing.

¹) In practice, you need to go at speeds for this, that are magnitudes higher than anything humanity has ever achieved.