Could monoamine oxidase increase be a solution for psychosis? If so how could I enhance it naturally?

Plz see psychiatrist. Combining this question together with your earlier one about dopamine, it sounds like you're interested in helping yourself (or someone you know) with psychosis -- but maybe trying to do this on your own? A psychiatrist is trained to help by assessing clinical situation, suggesting further diagnostic studies, & prescribing medications and/or other treatments -- as well as adjusting as needed.
Probably not helpful. Increasing monoamine oxidase activity, would reduce all monoamines, including serotonin, norepinephrine, and dopamine. Rauwolfia serpentina, a plant used in Indian medicine to treat psychosis acts by depleting all monoamines. It does treat psychosis, but also tends to cause severe depression, sometimes leading to suicide. See also: reserpine. For psychosis reduction you want to reduce dopamine.