I'm taking lisinopril 20MG how long does it take to get into your system?

Not sure what you mean "get into your system"

It gets into the system right away, but will take several weeks to have full effect. Even changes in dosage will take several weeks for a full effect

Lisinopril 20 mg Tablets (http://blood-pressure.emedtv.com/lisinopril/lisinopril-20-mg-tablets.html)

I didn't know if I took too much if it would lower my blood pressure to low right away and for how long it would keep it low.

If you took too much, it could perhaps kill you.

No taking too much will not make it lower faster, read the link I gave you, even taking larger doses still takes time to adjust blood pressure.

Follow the instructions of the doctor,