to fix,solve

수리하다

repair

고치다

fix (basic, still used)

복구하다

restore (systems, data, infrastructure)

보수하다

maintain/repair (formal, buildings/infrastructure)

해결하다

solve (most important TOPIK verb)

처리하다

handle (problems/issues)

조치하다

take measures (formal response)

개선하다

improve (fixing system/condition)

수정하다

correct/edit

바로잡다

rectify (wrong information, mistakes)

정정하다

correct officially (data, statements)

안정시키다

stabilize

정상화하다

normalize (return to normal state)

회복하다

recover/restore condition

정비하다

reorganize/improve system/structure