so lost after not being here for ages

[Terpe]

If i understood it right,visa is for 27 months, and out of that 27 months i should spend 24 months within UK and the rest of 3 months out of UK.

MLH, that's completely wrong.
You do NOT have to spend time out of UK. Complete nonsense, who told you that?

Stop worrying right now.
Even the 24 months living in UK qualifying period does not require you to stay totally here in UK

Enjoy your holiday