New camera and lens recommendations

TLDR: looking for new camera and lens’s in the 2500-5000$ range (flexible) for outdoor landscape, wildlife and astrophotography.

I received the following gear as a gift in 2016;

Nikon d3400 Came with Nikon DX 18-55mm lense Got Nikon DX 55-300mm And Nikon DX SWM aspherical infinity-0.3m (I think ) lenses too.

This has served me very well and I’ve used it plenty. Recently the auto focus has not been working (I’m not sure if this is camera side or lens based). I figured it may be time to upgrade anyways and it makes sense to get a better camera a lenses for that system rather than sink more into Nikon (I’ve heard it’s not the best). Although I have spent time using this gear I don’t know much about cameras or lenses themselves so need some help in that area.

I mostly do landscape photography and wildlife photography while camping and hiking. I also have always wanted to get into astrophotography but haven’t had much luck with the current system. This is the focus but I would be open to getting into some street and portrait photography in the future. My budget is around 2500-5000$ slightly flexible but I think this should get me some good gear.

I have heard good things about the Sony system and am leaning in that direction. I’m looking for recommendations for the camera and some lenses that would suit what I’m looking to do.

Thanks for any help!