Microsoft Lumia phone 640 xl LTE was running slow and malfunctioning

[Windows Central Question]

Microsoft Lumia phone 640 xl LTE was running slow and malfunctioning, updated to windows 10. worked well for 2 weeks and problems started again, what am doing wrong and what should I be doing?

 

[Guytronic]

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I had a similar experience with a 640XL.
Slowdowns can be caused by older apps installed on a phone designed to run WP 8.1

I noticed the phone becoming very sluggish after installing Instagram.