Okay, let's fill in the blanks with the correct tense. Here's the completed letter:
Dear Bob,
I **am writing** to you from Italy. I **am** here on holiday with my friend Lynn. We **are visiting** her parents in Rome. It **is** very hot today and the sun **is shining**. We **are** very busy this week. There is a big family dinner on Wednesday and we **are trying** hard to have everything ready. Now Lynn **is listening** to music and I **am swimming** at the sea. We **are having** a good time here.
See you soon,
Best wishes,
Tom
**Explanation:**
* **am writing**: This describes an action that is happening right now. Hence, we use the Present Continuous.
* **am**: This is the verb 'to be' in the present tense when used with 'I'. It describes a state of being.
* **are visiting**: This also describes an action happening around the time of writing the letter, not a regular routine, so we use the Present Continuous.
* **is**: This is the verb 'to be' in the present tense when used with 'It' (third person singular). It describes a current condition.
* **is shining**: This describes a temporary condition of the sun at this time, so we use Present Continuous.
* **are**: This is the verb 'to be' in the present tense when used with 'We'. It indicates the current state.
* **are trying**: This describes an action that they're doing during this period of time, so we use the Present Continuous.
* **is listening**: This is an action that is happening right now, so we use the Present Continuous.
* **am swimming**: This is an action happening at the moment, so we use the Present Continuous.
* **are having**: This describes what they are experiencing now, so the Present Continuous is used.