אם נשאר הרבה אוכל, אפשר להקפיא אותו היום ולהפשיר אותו מחר.

Here נשאר means is left / remains. In this verb, the masculine singular present form and the 3rd-person masculine singular past form look the same: נשאר. The context tells you how to understand it.

In this sentence, because it starts with אם and then talks about today and tomorrow, the natural meaning is if a lot of food is left over.

You could also hear אם יישאר הרבה אוכל, which makes the future meaning more explicit.

Because the subject is אוכל (food), and אוכל is grammatically masculine singular in Hebrew.

So the verb agrees with אוכל, not with הרבה.

• נשאר הרבה אוכל = a lot of food is left
• נשארו הרבה מנות = a lot of dishes/portions were left

Even though a lot of sounds plural in English, the Hebrew verb follows the noun that comes after הרבה.

Because אוכל usually works as a mass noun, like food in English. It is not normally counted item by item.

So:

• הרבה אוכל = a lot of food
• הרבה מאכלים = many food items / many dishes

Both are possible, but they mean slightly different things. The sentence uses the more general mass-noun idea: a lot of food.

אם means if and introduces a condition.

So the structure is:

• אם נשאר הרבה אוכל = if a lot of food is left
• אפשר... = it is possible / you can...

This is a normal real-life condition, not something hypothetical or contrary to fact. It is basically saying: if this happens, this is an option.

אפשר is an impersonal expression meaning it is possible, one can, or very naturally in English, you can.

So:

• אפשר להקפיא אותו = you can freeze it
• literally: it is possible to freeze it

Hebrew often uses this impersonal style instead of saying you directly. If you wanted a personal version, you could say:

• אתה יכול להקפיא אותו
• את יכולה להקפיא אותו

But אפשר is more general and neutral.

Because after אפשר, Hebrew uses the infinitive form of the verb.

• להקפיא = to freeze
• להפשיר = to thaw / defrost

The prefix ל־ is the normal marker of the infinitive in Hebrew.

So where English says you can freeze it, Hebrew is structurally closer to it is possible to freeze it.

Because one אפשר can govern both infinitives:

• אפשר להקפיא אותו היום ולהפשיר אותו מחר

That means:

• it is possible to freeze it today and thaw it tomorrow

Hebrew does not need to repeat אפשר before the second verb. The ו־ on ולהפשיר simply connects the second action to the first one.

אותו can mean him or it, depending on what it refers to.

Here it refers back to אוכל, which is masculine singular, so אותו means it.

Hebrew uses the same object pronouns for people and things:

• ראיתי אותו = I saw him / it
• הקפאתי אותו = I froze it

So even though food is inanimate, אותו is exactly the right form.

Because אותו already functions as the direct object form.

So Hebrew says:

• להקפיא אותו not
• להקפיא את אותו

For learners, it helps to treat אותו, אותה, אותם, אותן as complete direct-object pronoun forms.

Also, be careful not to confuse:

• אותו = him / it
• איתו = with him

They look similar but mean different things.

It is repeated because both verbs take the same object:

• להקפיא אותו
• ולהפשיר אותו

Repeating it is the clearest and most natural version, especially because היום and מחר separate the two verbs.

If you drop the second אותו, people would probably still understand you, but the full version sounds better and more standard:

• אפשר להקפיא אותו היום ולהפשיר אותו מחר

Yes. Hebrew word order is flexible, and time expressions can move around.

The sentence as written is very natural:

• אפשר להקפיא אותו היום ולהפשיר אותו מחר

But you could also say things like:

• אפשר היום להקפיא אותו ולהפשיר אותו מחר
• מחר אפשר להפשיר אותו

The original order is common because it keeps each time word close to the action it belongs to:

• freeze it today
• thaw it tomorrow

Because הרבה אוכל means a lot of food as an indefinite quantity.

If you said הרבה מהאוכל, that would mean a lot of the food, referring more explicitly to a specific known set of food.

So there is a useful contrast:

• הרבה אוכל = a lot of food
• הרבה מהאוכל = a lot of the food

In the sentence you gave, the more general הרבה אוכל sounds natural.