So my bathroom sink was draining slowly. This seems to be a constant issue with this sink..I have poured liked plumber down it numerous times and it works for a week or so and then needs to be done again. This time I was having no luck with the chemicals. I took the trap off and it was pretty funky. Cleaned it and I think I have everything together correctly but it seems like it is draining even slower now...any suggestions? This photo shows how the trap was put back together except that the two joints are much closer together, like basically touching
You may have a larger clog farther down that sink drain. Try another large dose of drain cleaner down that sink, then let it sit 6-8 hrs with no water use. After 6-8 hrs chase it with several minutes of hot water. This added soak time has cleared several slow drains for me. If this doesn't work you may have to snake the drains, working from that sink downward.
That looks like a DIY or (cheap) trap. As it will work the same even if the ends are swapped , I might look at the sink itself.
Not long ago I found a sink that had clear drains and a good vent but was draining slowly.
I filled the sink with hot water until it started to slow then used a toilet plunger , what pumped out of the sink vent was so gross, i don’t want to say what it looked like but after a couple of plunges it started draining better. I had cleared the trap and drain with a small power auger, it was only after plunging that the in sink vent cleared and it drained well, after it started draining I filled it to the sink vent level and let it run on hot for a while to make sure it it was clear. This is in a rental so I don’t know what was plugging the sink vent and it was my first experience like this but a plunger with hot water may help you as it did me. Once the vent started to clear I plugged it with my finger while plunging prior to over flowing to the vent for everything I did. Hope this helps.