Actually, slowing down & speeding up time is not only possible, but it’s proven. Gravitational time dilation is the theory that gravity affects the flow of time, the stronger the gravitational field, the slower time flows in it. This has been proven to some degree by comparing stationary atomic clocks to ones in airplanes & satellites.
Don’t use the phrase “strings” when you talk about dimensions, otherwise people might think you’re dumb enough to believe string theory.