$Berkshire Hathaway-B (BRK.B.US)$ why is it dropping?

$Invesco QQQ Trust (QQQ.US)$ is it good to enter now?

$Apple (AAPL.US)$ 
I have been an Apple iPhone user since touch screen phones came into life. As a simple person, I have always love simplistic features and iPhone is just about it! I am truly grateful that it exists! Year 2020, I got my hands on iPhone 11 Pro on the last day before the lockdown. I remembered rushing to own it as I know deeply I will be grateful to have it throughout this Covid period and it certainly lives up to its name. =) It has done so many things for me...photos, videos, video calls, voice recording, keynote editing, online presentation, graphic designs, online shopping, even google classroom for my kid. I would never be able to imagine living through the lockdown without it. Thank you, APPLE! ...