Learn English – use “past tense “and “future tense” in one sentence

As FumbleFingers mentions in his comment, this structure is fine and not uncommon. In English, we often modify the sentence to match a particular perspective, in this case the perspective of Elena, from the future, looking back over something I did in the past. This in comparison to:

Elena will correct me if I miss something important.

This perspective is of me, looking forward to something I will do, which Elena will later correct.

This can be tricky and can be ambiguous without good time markers. Although you provide this information in your question, in your actual example it's not clear if you will miss something in the future (from when you are speaking) or you've already missed something in the past. In casual conversation, this information might not be important or you might have already provided context in the previous sentence, so it's not a big deal. Just something to think about.

Consider these two examples:

Elena said she will correct me if I miss something important.
Elena said she will correct me if I missed something important.

Because I'm indirectly quoting Elena, it's more apparent that, if I say "miss". it means I will do the task in the future, and "missed" means I've already done the task.

Of course, this assumes that everyone chooses their words carefully instead of talking as they are thinking. Native speakers often say sentences with confusing or ambiguous verb tenses, and you have to parse the actual meaning from context.

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.