If the tablet is charging when the cable is connected, and the tablet shuts down after unplugging it, then the most likely problem is that the battery is dead. Look at the solution for fixing dead battery issues.

If tablet turns off after charging cable is disconnected, or if tablet does not turn on at all, then you should replace the battery. To do this, remove the tablet's back cover. There you should see the battery. After replacing the battery you should put the cover back on. Then test to see if your tablet is working by turning it on.

The speakers are distorted, and the noise crackles. The sound does not work at all.

Dirt, debris, or other grime might be stuck in the speakers or speaker housing. Try to gently use a cloth and wipe away anything on the outside, blow or used compressed air, and very lightly go over the speaker. This will help clear any grime out of the speakers and then test the sound again. If they are still not working, then you should try replacing the speakers.

The speakers can be replaced, and new ones should perfectly work. Remove the back cover of the tablet and find the speakers. Remove the screws, pull them out and disconnect them from the battery. Connect and screw the new speakers. Put the cover back on. Test the audio to make sure the replacement was successful.

WiFi signal is weak, slow, and/or spotty.

Other electronic devices, such as microwaves, may create interfering radio frequencies. Try switch to the 5GHz WiFi band. (Will show up as a separate access point in list of wireless networks)

Having the wireless router far away, in a different room or in a cabinet can degrade signal strength. If possible move the router to a more central and open location. Another option is to install a wireless repeater in an open area to boost signal strength