If you are looking to speed up your Android pone or Android tablet, you should download an app called "DU Speed Booster" which does work wonders when your phone or tablet is slow. DU Speed Booster does have some features which helps in freeing up space and memory for the phone. It has "CPU Cooler" feature which cleans up the apps using phone CPU. It has "Trash Cleaner" feature to clean up system trash and other unimportant files. It also has "Phone Boost" feature to free up the phone RAM memory space so that your phone can run faster. Another helpful thing is if you can tap on the circle in the center of the phone app, the app will do a overall general boosting.
Now when it comes to the question of whether you should update your phone operating system, you should only do it if there are some critical security updates or fixes. Of course, the phone manufacturer would recommend that you update every single release of their software updates but you need to know that this will slow down the general speed of your phone. Even Apple had admitted to slowing down their Iphone for users every time, the users updated their software operating system. That was done to encourage people to buy a new phone sooner because they will find their current phone to be too slow in processing any work. This applies to other Android phone manufacturer such as Samsung, LG, Huawei, Google phones and other companies phones. So unless if it is a major and critical updates, i do not usually update my phone's operating software system.