Sure, I'll provide the correct forms of the verbs in brackets to complete the sentences. Here is the expanded version with explanations:
We usually go to my grandmother's house on Saturdays, but today we are staying at home.
- "Go" is used in the simple present tense to describe a regular action.
- "Are staying" is used in the present continuous tense to describe an action happening right now.
It usually rains on Bonfire Night, but this year it is not raining.
- "Rains" is used in the simple present tense to describe a habitual action.
- "Is not raining" is used in the present continuous tense to describe an action that is not happening at this moment.
What are you eating? Can I have some?
- "Are you eating" is used in the present continuous tense to ask about an action happening right now.
We always celebrate my dad's birthday in a restaurant.
- "Celebrate" is used in the simple present tense to describe a habitual action.
I can hear music and people singing. What are they celebrating?
- "Are they celebrating" is used in the present continuous tense to ask about an action happening right now.
My sister speaks three languages - Russian, English, and French.
- "Speaks" is used in the simple present tense to describe a general fact.
He is speaking to someone on the phone at the moment.
- "Is speaking" is used in the present continuous tense to describe an action happening right now.
In summary, the simple present tense is generally used to describe habitual actions or general truths, while the present continuous tense is used to describe actions currently in progress.