How can I use /timings paste to figure out what is causing lag, and how can I use this into to fix it?
Timing thing in your server not always is going to help you improve your server performance. Timing things you can know what thing are costing you more time to run. If for example a plugin has an awful timing you can notify the developer or you can modify the plugin to improve performance, but not always is going to be the plugin
In the timings.aikar.co link, spot the red numbers. They mean your server is severely lagging because of them (especially if they are run very freqiently).