Samsung care and we are here to help.
Please check and follow steps below:
1) Outdated Updates and/or incomplete Software updates.
2) Weak/Low Network Signal.
3) Weak/Low Router / Wi-Fi Signal.
4) Phone overheating due to more apps running in the background.
5) Full cache
1) Complete the device update to the latest Software updates and at the same time, both FB & Messenger apps keep up-to-date.
2) Check with Network Provider about the status of signal of your coverage area.
3a) Re-position your phone towards the stronger signal from Router by checking Router settings and avoiding wall/barrier.
3b) Strengthen Wi-Fi signal by re-positioning your phone and check/rectify Wi-Fi settings.
4) Close All Apps running in the background.
5) Clear the cache and reset your phone device.
If the problem persists, please bring your device to Samsung Authorized Service Center nears you.
Meanwhile, to get the timely support through your fingertips, please download and install Samsung Members app.
Hope this content is helpful to you and your problem gets solved.