Hi my 2003 focus randomly overheated a few months ago, i thought it was because I ran out of water so I topped the car back up but 5 mins later it had drained all the water again. I limped it home and filled it up again I ran the engine for 20 mins monitoring what happens there was no leakage under the car or in the engine bay. It starts and runs but after about 20mins the water has gone and the car overheats and I have to refill it. Does anyone have an idea what the problem is?

sounds like the expansion tank cap needs replacing. Basically the heat causes the steam to be generated, the steam escapes as there is not sufficient closure around the cap. As the steam escapes almost invisibly you never notice...

Hi my 2003 focus randomly overheated a few months ago, i thought it was because I ran out of water ...

Aha, a chicken-and-egg problem: did the water leak causing overheating, or did the car overheat, causing a water leak?

...so I topped the car back up but 5 mins later it had drained all the water again. I limped it home and filled it up again I ran the engine for 20 mins monitoring what happens there was no leakage under the car or in the engine bay. It starts and runs but after about 20mins the water has gone and the car overheats and I have to refill it. Does anyone have an idea what the problem is?

Check the thermostat. It could easily be something else, but if it is the thermostat, at least the course of action is fairly straightforward.

Run the car on the drive, paying close attention as it starts to warm up:

i) Any leaks, even small ones, as it warms up?

ii) As it gets to the point that the temp gauge (and what is it doing during this time? anything unusual?) moves off the stop, it should be hot-ish on one side of the thermostat and cool on the other. Then, suddenly, there should start being water flow and the temps on the two sides being more even.

iii) If the car boils over without evidence of water flow having got going (eg, top hose warming up) then probably the thermostat (or water pump) has a problem.