Feedback on the Lenovo B490 - Wifi Problem

Hi,

  I m using the Lenovo B490 Laptop with Ubuntu 16.10. Here I m facing the Wifi problem lot more. Its shows the available list of Networks, if i connected with one network mean it will take more time to connect and its asking for password more times. if its connected also the network speed is very very slow(Dead slow). I dont know what to do. In this campus i can use only wireless network. What should I do?