Your phone's screen will not respond when pressed. Here is a guide on how to remove the screen.
Your phone's screen may be dirty and therefore does not register your presses onto it. This is easily solved by simply using a damp rag to wipe the screen clean followed by a dry rag to remove any left over moisture.
Your phone may have booted up wrong or other slight malfunctions. Try powering down your phone and waiting 20 - 30 seconds before rebooting as this will allow anything running to stop. If your phone will not manually shut down then remove the battery from it and follow the above instructions.
Screen pressed against surfaces
If your phone's screen is pressed to hard against surfaces, setting it face down and putting something on it or even just being in your pocket and pressed against you or a wall while in there, it can cause screen failure on occasions. The best solution for this is preventative and to be cautious of applying too much pressure to the screen, though we can not always be thinking of this the best way to fix it if this does happen is to restart the phone and hopefully that will fix it. If that does not solve it then follow the steps for Circuitry failure listed above.
Phone does not charge/will not hold a charge
Your phone will not charge when the charger is plugged in or the battery drains extremely fast. Here is a guide on how to remove the battery.
Sometimes the problem will not be the phone but instead the adapter, charger, wall socket, or other power source you are using. First thing would be to try a different plug in whatever you are using and see if it will work or trying a different adapter if you have another around. This is the best thing to try first before messing with your phone's settings or internals.
The problem may be that the battery is overheating during it's charge so it will not charge or hold the charge afterwards. To help solve this try removing the battery from the phone and letting is sit out for about 15 minutes to help cool it down and then place it back into the phone and try charging again. To avoid overheating the battery do not run several heavy processing apps or try to play games/use your phone while it is charging as it will cause the battery to heat up very quickly.
If nothing you do seems to get the battery to hold a charge or charge at all it could be a defective battery. If this comes to be the case then you will need to purchase a new battery to replace it though going to your local phone dealer and having them test/check the battery first would be a good idea as not to spend money if you do not need to.
Phone will not connect through Bluetooth
Your phone will not connect to other devices through Bluetooth or is not being discovered by the other devices.
Not following the correct pairing process
Make sure you are following the pairing process correctly as skipping any of the steps or trying to do it a different way could cause the device and your phone to not connect properly.
Device is out of range
Make sure that the device is close enough to your phone so that it will connect. While Bluetooth does reach out a decent range sometimes the devices need to be close if not within arm's reach of each other to first connect.
Wi-Fi Router interference
Sometimes if you are close to a router it can interfere with the connection process. Try moving away from the router and away from anything else providing a large signal from a source.
Applications run slowly on phone
The applications you try to run on the device operate slower than usual/expected.
Small Memory Space
Since the phone only comes equipped 8 GB of memory space ( 4.14 GB of usable memory according to LG's device page of the LG Power) it is highly probable that you are low on space which will slow down all processes on your phone. If you can obtain an SD card to install and add extra space which to download all your apps this will help free up space and quicken your phone.
Unused apps will take up space and eat your memory. If you are not using any apps deleting them will help solve your problem most efficiently.
Apps are Unmanaged
Your apps can run in the background and take up space and processing speed. Some apps can help fix this problem, such as Greenify, and will allow you to put them to sleep so they will stop running and taking up your speed.