I am new to photography profession. i have started wedding photography shoot and i brought Sony A7S II (4K) camera. i am confuse in buying the lenses for the same.So please suggest me the lenses that will be best for wedding photography.
I don't know what 16-35 2.8 you're referring to, because Sony hasn't released one yet. There are some strong rumors that it will become available this summer, or you might be talking about an adapted one. Either way, it would not be my choice for weddings. It's difficult to take good portraits with wide angle lenses because of distortion. Until you fully understand these limitations and know how to work around them, it's best to avoid them.
The 50 1.8 is fine, a good all-around lens, works well for portraits and opens up wide in low light. But it's a prime lens, which means it doesn't zoom in or out. For weddings this can be difficult, especially when things are happening on the other end of the room and you can't run over there fast enough. Between the two choices, though, that's the better one.
If I could have only one lens for a wedding, it would be a 24-70 2.8. The aperture opens up wide for low light work, it has a very useful focal lengths in the zoom, and the one from Sony is excellent. You might even be able to get away with the 24-70 f4 lens, which doesn't open as wide in low light, but you can compensate with a higher ISO because the a7sii is the king of low light.
I just bought a a7r ii. I got a Zeiss 24-70 f4 and rokinon 85 mm f1.5. the Zeiss has very nice bokeh for only being a f4 and the 85 is in case I need a lower aperture for low light situations. The 85 is manual but it's cheap and the glass is nice. Good for portraits where you can get folks to hold still for a moment and focus carefully. The 24-70 has really fast auto focus and can be used for candid photography that you need to catch on the fly. I have this set comboed with an a77 with a Tamron 17-50 f2.8 and a 70-200 f2.8. For weddings a 70-200 comes in very handy, especially on a crop sensor which essentially makes it reach go up to 300mm. You can be way in the back of the crowd and still get those great shots during ceremonies without having to disturb the crowd. I also have a Minolta 50mm f1.7 that's nice for portraits and you can pick one up usually for $100 or less.