Issue with your Apple Device??
Battery Problem?
In this case battery may be need to replace. In rare cases the charging IC may be the cause.
Damaged Screen
Screen replacement needed.
Liquid Damage
Common Liquid Spill Damage Symptoms: System not turning on, System freezing, Screen color damage, Keyboard malfunctioning
Power Adapter problem?
In this case IC of the adapter need to replace or the adapter replacement needed.
Need Upgrade?
Some times processor lacs behind for the task you want to do on your system. The upgrade will solve your problem.
Slow System?
System can be slow for many reasons virus, malware, junk files, unneccessory processes running.