That Lenovo tablet was pretty low end from the start. If you have the 8 GB model, you probably have maybe 5.5 GB for usable user storage (apps and files) which can fill up quickly. If you have a lot of media, you could put them on an SD card, but it's only a temporary measure as user space tends to bloat over time. Can you uninstall any apps you're not using?
Social media apps are the worst in terms of bloat, but you could always get rid of Facebook, instagram, etc. apps and access them through the browser.