still can't clean quartz countertops - what am i doing wrong?

If it's streaky, it's probably soap left behind. Warm water and a drop of washing up liquid, then go over it again with a cloth wrung out in plain water, then dry it with a microfibre. Most people skip the rinse. For anything dried on, a plastic scraper rather than scrubbing. And keep bleach, oven cleaner and the scratchy side of the sponge off it - quartz is tough but the resin in it isn't. Is it streaks or actual marks you're fighting?