MacBook Pro boots up really slow

Hello everyone!

I have a couple of issues with my MacBook Pro and I was hoping someone could help me.

It's about a mid-2010 i7 2.66 GHz MacBook Pro, 8 GB ram, running Mavericks.

The problem is as follows:

My MacBook takes between 3 and 6 minutes to boot up. It is the kernel stage that takes really long. The rest is fine. Besides that, the battery is also empty very quickly. After about 1,5 or 2 hours of surfing on the internet, the battery is empty.

I recently put in a new battery because the other one said it should be replaced. I hoped this would fix the battery issue and maybe even the boot up issue, but unfortunately the battery is still empty very quick and the boot up is still slow.

I think the boot up started to get slower around a year ago. It then took like 1 or 2 minutes instead of the couple of seconds it used to take. About half a year ago that boot up time significantly got worse. And I think it may have gotten a little more worse after I installed Mavericks a little less than half a year ago.

Besids that, there are a few more issues. I'm not sure though if they are related to the slow boot up or to the battery.

When I connect or disconnect the adapter to my MacBook Pro, everything freezes for a while. I usually can still move my cursor around, but video or audio freezes and I can't open new windows or something like that. The freezing takes between 30 secs and 2 minutes. This is something that started to happen about a little more than half a year ago I think.

Also, when I try to save something, a document or an image from a website, it takes a while for the Finder-popup to show my folders. It used to immediately show all the folders, but now it takes a while to load them. This is something that started to happen a couple of months ago.

I honestly have no clue why these things are happening.

I already checked my harddisk. I used Disk Utility and then the First Aid tab to check my harddisk and everything is fine. I also have over 100GB still available, so the harddisk is not too full or something.

I also checked the activity monitor. I'm not too sure what to look at on the monitor, but as fas as I can tell, there is nothing strange going on.

I also already reset my PRAM and SMC.

Does anyone have any idea how to solve these problems? Or maybe just point me in the right direction?

Many thanks in advance!