During the COVID-19 outbreak, delivery apps have become very common in Korea.

Statistics show that more than a half of Koreans use these apps.

In the past, the qualitiesy of the goods were not verifieddelivered was inconsistent, so I cadidn't trust them.

This sentence is pretty ambiguous, so my correction is based on my own guesses. What do you mean by the "good were not verified"? Do you mean, the apps or stores weren't regulated, or delivery drivers themselves didn't verify what they were delivering?

As a result, I used offline stores rather thanpreferred brick & mortar stores to online ones.

Alternatively, "I preferred shopping in-person rather than online."

Now, the delivery systems aresystem has been much improved, so I can trust trading goods withbuying and selling on these apps.

Since I don't need to go out byleave my house when I use the app, I can save my time for shopping and I don't need to consider preventworry about catching the virus.