Past continuous or past simple he/sit down/on a chair/while/I/paint/it

He was sitting down on a chair while I was painting it. - Он сидел на стуле пока я его(стул) рисовал.

Was sitting- форма Past Continuous Tense от глагола to sit;

Was painting - форма Past Continuous Tense от голагола to paint.

Если используется слово \"while\", то в обеих частях предложения ставится Past Continuous.