Problem with Intel(R) Wireless-N 7260 which works very slowly

Hi,

I'm a new user of Lenovo ThinkPad E540 with Inter(R) Wireless-N 7260. Unfortunately, I have some problems with wireless access. Sometimes my laptop loses Internet connection. If it finds  a connection, it works very slow. My old laptop had 20Mb/s of download speed, bu the new one has only 3Mb/s. I'm really disapointed. I have installed all drivers. Everything is up to date. I work on Windows 8.1 64bit. Please help me because that issue drives me crazy. Sorry for my english

Inter(R) Wireless-N 7260: http://www.speedtest.pl/test/92556052

Should be: http://www.speedtest.pl/test/92557087