3 Problems using WhatsApp-

Im new to WhatsApp- & having problems-

1- Both me & my friend are using Samsung Phones- but the problem maybe on my end because mine is Old & his is Fairly new- we both have whatsapp installed- when I ring through whatsapp - his phone does Not ring- but I can hear his phone ringing - how can we Fix this ???
2- when I send him a text message/msm through whatsapp this message displays on his phone Only 2 seconds & then Disappears - How can we fix this ,so it stays until he deletes it ???
3- when I click call or Video call - through whatsapp - my microphone has got a line going through it -even though I gave whatsapp Permission to use my camera & Microphone - how can I fix this ?? how can I fix this ??