how could I say "متخاصمين

Hi Dina, try,
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- They had a quarrel.
- They are angry with each other.

A quarrel (with somebody / between A and B) (about / over something): an angry argument or disagreement between people, often about a personal matter:
'They had a quarrel, but they're friends again now.'
'In spite of their quarrel, they remain the best friends.'

Hello Dina,

At the moment people have a quarrel or a disagreement they are called "opponents".