It's a problem with the camera and phone not agreeing on how to manage the pairing. It appears to only affect phones from Oppo, OnePlus, and any other brand that uses the same oppo/OnePlus version of Android. My xt-5 was broken by a recent firmware update in exactly the same way. As far as I'm aware it's a problem with the camera firmware NOT the X-App. It's disappointing (to say the least) that this isn't going to be fixed. Also the remark that it only works with stock android is nonsense, since there are plenty of people out there with Samsung phones. What they meant was, we can't be bothered to test it on ColourOs. It would appear that Fuji are, gradually ensuring that ALL their cameras don't work with ColourOs which doesn't seem like the smartest move...

That is typical for the X-T5, I was having a significantly worse hit rate before the last two firmware updates. A non-moving scene with a clear, central subject, plenty of light and contrast, single point AF in S mode, completely out of focus (even though it gave focus confirmation in the viewfinder) . That was with modern lenses like the XF 18/1.4 and Viltrox AF 13/1.4. It was occurring more like one in 20 photos. I still have wildly varaiable results with the XF 150-600 and C mode AF when shooting birds, sometimes it's better to have subject detection (bird) off, sometimes on. It's very frustrating out in the field and has lost me several lifetime opportunities. I like to 40MP sensor and the results when it works well, but I contemplate selling the X-T5 and purchasing an X-H2S in it's place. That seems more economically sensible than a wholesale switch to another brand for bird photography. Additionally, the recently publicised tech documents from Fuji about the AF and settings for various subjects and lens types seems to have made my X-T5 and XF 150-600mm slightly to moderately worse for bird photography.

The XF 70-300 seems plenty sharp to me, it might need some practice and familiarity to get the best out of it (like all longer telephoto lenses). It's very good value too. It isn't something for street photography though, that is usually done with shorter lenses (think 16, 18, 23, 27, 35, 50mm from the Fuji prime line-up). Longer lenses drag the background into the scene flattens the space, and the long working distance reduces the feeling of being in the scene.

im doing photograph stuff for my club, is not good for me to stay close to the people im shooting.i also want to try street photography

I’ve really enjoyed my 70-300 on my X-T5.  What kind of photography and what subjects?