en_tn_condensed/rev/11/19.md

Then God's temple in heaven was opened

This can be stated in active form. Alternate translation: "Then someone opened God's temple in heaven" (See: rc://en/ta/man/jit/figs-activepassive)

the ark of his covenant was seen within his temple

This can be stated in active form. Alternate translation: "I saw the ark of his covenant in his temple" (See: rc://en/ta/man/jit/figs-activepassive)

flashes of lightning

Use your language's way of describing what lightning looks like each time it appears. See how you translated this in Revelation 4:5.

rumblings, crashes of thunder

These are the loud noises that thunder makes. Use your language's way of describing the sound of thunder. See how you translated this in Revelation 4:5.