What is wrong with my laptop?

I'm currently using a Windows 7 Lenovo and I'm afraid of what's happening to it.

I'm not sure if this is because of the internet, but chrome itself is very slow. I have to wait for a long time for that new tab to actually open when I click it. The buttons in a lot of websites are not responding (it says I clicked it, but nothing happens). It lags when I scroll down, and the words I'm typing are lagging behind.

I was even more scared when I realized my laptop was slow. I move my mouse around my desktop and the square highlights of each icon is struggling to keep up with my mouse. When I play a video, it takes a long time to process and lags. The audio comes out in a laggy, static effect. Programs take some time to open, and when I refresh my desktop, it freezes for a couple of seconds before coming back. (Even my games have lag and terrible audio)

And to think yesterday, everything was working well, fast, and normal.

I don't think this is because of my memory, because the amount I have used up is less than half.

If possible, please don't let me download anything, but if you insist, then I'll give it a try.

Thank you for reading this, and please answer. The first method to work will be chosen as best answer.

It would be 100x easier if you provided the exact name and model of the computer so I could look it up and look at the specifications. Of if you provided us how much money it is. But from
What it sounds like is that it doesent have that great of parts. Such as the proscesser, ram, and other stuff. It can't handle all that stuff because it isn't good enough. I have a old hp laptop and have every problem you have. All I use that's close to a laptop is a iphone and I just use it for the internet. But I'm getting a new gaming laptop soon. So my advice is to get a nicer laptop. Geta MacBook or a asus laptop. A good asus laptop is for 950 bucks. That's what I'm getting

Back up your user data and perform a factory restore. This will delete all the contents of your hard drive and restore it to the way it was when it shipped from the factory. Once the restore is complete, install your AV of choice. Kaspersky and BitDefender are the top 2 paid products. Avast, AVG and Avira are the top 3 free products and your laptop probably came with a trial version of Norton's or McAfee installed. The trial period will be reset when you perform a factory restore, allowing you to go about a month before making a final choice. Once the AV program is installed and updated, perform Windows update until you get no more updates. You will probably have to reboot a good 3 or 4 times before this is done. Having completed the updates, make certain that you have the latest driver versions and any firmware/BIOS updates installed. You can now restore your data and install any 3rd party apps. At this point your computer should be running as well as it did the day you purchased it.

To see if you have adequate RAM, open Task Manager and click on Performance. Now click on Resource Monitor and then click the memory tab. Load all of the programs you normally run and look at the available RAM on your system. If you have no more RAM available you should probably consider adding more.

Ttry to change your window or you can try
msconfig startup>disable startup apps you don't require
and remove the unwated toolbar and chrome extensions.

Firstly, use good antivirus, kaspersky antivirus will protect your PC.