Low wifi speed

Hello,

I bought vostro 7590 and have a problem with low wifi speed (only about 2mb/s). I also have my old lenovo laptop that connected to the same wifi network and  have stable connection around 25-30mb/s. Both computers are placed near each other on the same distance from wifi router.

Read that smartbyte might cause this problem but after deleting it problem still remains. Latest network updates also already installed.

Also I believe on the first day of usage wifi worked quite fine.  

Maybe i should change some settings or something like this?