Programs not responding,critical drops of fps in a game and more..

Hello everyone, I have a problem and I would be very happy if someone could help me. Recently i bought this laptop, a really powerful machine for its price(Lenovo Y50-70, if u want to know the specs). However, I'm experiencing problems already. When I started the laptop for the first time, it started windows for about 10 seconds. Later on the windows startup time started increasing. The laptop i bought actually came with a Windows 8.1 OS, which i didn't like much and changed it to Windows 7 Proffesional 64 bit.

First, the game I'm playing, World of Tanks, is a buggy game and i still run it with 80-120 fps on high settings. At first i entered the battle 5-10 seconds after the loading screen (with around 30 seconds to "prepare to battle" while the countdown stops) and now i enter sometimes 2-3 minutes later, which is ridiculous, because the game is only 15 minutes long and an average battle is 5 minutes. Also today when after loading ridiculously slow the fps meter was showing me 25-30 fps and it was so buggy...

Second, windows is really slow and programs dont respond. Im sure of that because a lot of times it just shows me that when i click on them because they kind of freeze and i want to see whats happening. Also the mouse is not working smoothly enough which is an indicator of something being wrong either with the operating system or the hardware. Thanks in advance. I would really appreciate if you could help me! :)

*Edit - I really wish this was a game issue, but it apparently isn't

Well as a matter of fact I had a virus in my system and I honestly don't know what the difference between malware, spyware and adware is, if you could explain it to me. So I had this virus called EID_pe_iscorrupted, or something like that. After another scan system with Avg it doesnt seem to find it, but my system is still slow, which can be two things: either the computer was slow before the virus and can still mean there could be hardware problems or there where other malicious software before that. Either way I'm not really happy, but I'll be doing a Windows 7 reinstall around December, so I will post here if that changed something :). Anyway, thanks for the tips.