Some people lose quickly. Some lose slowly. Neither rates of lose are wrong. It’s just how we individually react. As @catwoman7 said there are lots of factors that influence your rate of loss. What you can depend upon is the higher weight loss you experience the first few months doesn’t last & the closer you’re to your goal the more slowly you’ll lose.
Never heard that you stop losing at 6 months. I certainly didn’t. I hit my goal at 6 months but continued to lose for another year. Much more slowly in that year cause I was increasing my caloric intake to try to stop losing.
If your weight loss has slowed or stopped you may have hit your point of balance i.e. you’re consuming the number calories your body needs to function. If you’re gaining, it’s because the calories you’re consuming exceeds what your body needs. The only way to keep losing is to decrease your caloric intake &/or increase your activity level.
Everyone experiences small fluctuations in their weight. I’m pretty careful about my diet & my weight fluctuates about +/- 500g (about a pound up & down). It can be because I’m retaining fluid, constipation, an extra snack, a dropped snack, missed meal, adding a new food, etc.
Don’t give up yet.