difference between destroy and ruin

destroy - (устгах, юу ч гүй хиар цохих, хядах)"to destroy" means to completely ruin, put an end to something by damaging or attacking and If something is destroyed, it it likely obliterated or at least damaged beyond repair.
1 to damage something so badly that it no longer exists, works, etc.
destroy something/someone
       ---- The building was completely destroyed by fire.
2 to kill an animal deliberately, usually because it is sick or not wanted
     ---- The injured horse had to be destroyed.
ruin - (сүйрүүлэх, сүйтгэх)Ruined is damaged beyond repair but not yet destroyed.  Ruin has a similar meaning with destroy, except that the focus is on something becoming unusable, spoiled
1 to damage something so badly that it loses all its value, pleasure, etc.; to spoil something
ruin something
     ---- The bad weather ruined our trip.
2 to make someone or something lose all their money, their position, etc.
ruin someone/something
     ---- If she loses the court case it will ruin her.

difference between destroy and ruin

• "to ruin" is the physical destruction of. It can be used both literally and figuratively. Literally, 
  "falling bombs ruined the city". Figuratively, "Rain ruined her wedding day." 
  
  "to destroy" means to completely ruin, put an end to something by damaging or attacking. It can also be used literally or figuratively. Literally, "the boy destroyed the girls doll with a hammer until it was in pieces." Figuratively, "You destroyed my marriage" meaning you caused my marriage to end for some reason such as infidelity.

• ruin can also be nouns. Destroy is only a verb.

• If something is destroyed, it it likely obliterated or at least damaged beyond repair. Ruin has a similar meaning, except that the focus is on something becoming unusable, spoiled, or valueless. It might still be externally unchanged, but it has lost its value to a great degree.

• Damaged can be fixed. Destroyed cannot be fixed. Ruined is damaged beyond repair but not yet destroyed.