Role of "ho/हो" in sentences
मुझे देर हो रही है -- विलंब हो रहा है.
If the first part of the sentence is being spoken by a man, why is it रही and not रहा?
Also, why is हो used? Is हो supposed to be होना? Why isn't it है?
Another example: Umer Sharif haazir ho. उमर शरीफ़ हाज़ीर हो
Why isn't it है in this example?