The first sentence is basically correct. The second one is basically incorrect.
The first sentence is better expressed if you put the time phrase closer to the verb it applies to. So:
I went to the hospital last night and saw a patient being treated.
You can leave out the second "I" since it's understood.
Your second sentence has a few problems. First, rised is not a word in English. The past simple of the verb rise is rose, and the past participle is risen. Second, the sentence doesn't make sense, because the sun rises of its own accord: there isn't anything that can rise the sun.
So, here you would say this:
I will go to the hill tomorrow morning and look at the sun rising between the hills.
(The "in" isn't necessary.) Intransitive verbs can't take the passive voice: if you can't "rise something" then you can't say that "something was risen" by you. (The transitive version is "raise," e.g. "Jesus raised Lazarus from the dead" and not "Jesus rose Lazarus from the dead.")
Here's a sentence that correctly illustrates what you're trying to do:
I will go to the farm tomorrow and watch the cows being milked in the barn.
Someone will be milking the cows, therefore the cows will be being milked.
For some nice examples and exercises on this, take a look here.