Use https://gtmetrix.com/ as a starting point. I just analyzed your website and most of problems can be removed easily by doing some changes to the source code and/or server configuration. https://gtmetrix.com/reports/teknolojidenhaberler.com/TmNq2vxy
the best tool is google insights, you'll find all the information you need to make the speed of your website
Consolidate your JS files into a single file, the same for your CSS files. Get a better host (dedicated hosting is best), RackSpace is good.
Scan it under GTMetrix. It will point out weak areas and also with suggestions and steps on how to implement them.