p20 lite messenger notification issue!!!

[Android Central Question]

hey I bough phone new, now when I reiceived messenger and close from notification center it shows stil, when I open messenger still heard messenger sound and sms shows even when I swiped right or left. when I'm go messenger I hear messenger sound , on s5 neo, a5 2016 no problem, but in huavei p20 problem, I swiped left to close, after 5sec it still shows messenger in notification bar, or even when I go to messenger and shows messenger updates and heard sound, still shows previously messenger who wrote me even when I closed up notification and don't read that after 5sec still shows in notification bar , or even when I opened messenger app I got the same messages still sending now, but I got before 10minutes, on the top I see who wrote me, and what even when I swiped left to close from notification center. what is this???