He recovered after a long stay in the hospital.

Restore is a transitive verb.

Restoring health should be

his

health

be

repair

The whole sentence should be translated into

After ...

he

have

stay

exist

hospital

for

a

long

time

, his

health

be

Recovered.

or

have

stay

exist

hospital

for

a

long

time

, he

repair

his

Healthy. /

he

recover

from

his

disease