It's polite to explain why you are unable to accept an invitation or offer.
For example:
I'd love to but I'm busy, I'm visiting my sister this weekend. 

Everyday English with Teacher Alyse

Not Accepting an Invitation

آن روز که مرکب فلک زین کردند

آرایش مشتری و پروین کردند

این بود نصیب ما زدیوان قضا

ما را چه گنه قسمت ما این کردند

 I tell You this -- When, starting from the Goal,
        Over the shoulders of the flaming Foal
        Of Heav'n Parwin and Mushtari they flung,
        In my predestin'd Plot of Dust and Soul.


قسمت = fate


Persian Poetry

آن روز که مرکب فلک زین کردند

You will know some reasons why Colombian coffee is so successful

1. Especie y variedad

2. Investigación

3. Madre naturaleza

4. Cosecha manual

5. Beneficio húmedo

Remember that I teach Spanish on italki, you can book a class for more information you can look at it on my profile :)

Colombia

5 razones de por que el cafe colombiano es tan exitoso

CHISTES MEXICANOS

DICHO MEXICANO 4

Want to crush it at your next social event? We've got your back!
This episode of Spanish Unplugged will give you the phrases and tips you need to break the ice, understand local humor, and join the conversation at any party or gathering.

🎙️ Dive into the culture, language, and all the socializing tricks you need to make a great impression!
💡 Want this guide? Drop me a message and I’ll send it your way!

Spanish Unplugged Podcast

EP9: Ice Breaker Master: No More Awkward 😎

В чём секрет изучения иностранных языков? Практикуем ежедневный русский на базе текста. Медленный темп.

SuperRussian B1-B2

1. ЧАСТЬ 1: Секрет изучения языков

In this episode I talk about what I have been up to this last week, I include some idioms and phrasal verbs you might not be familiar with. I am always looking for italki learners to be guests on my podcast, so if you are interested, feel free to contact me anytime. 

Kev's English Podcast

KEP Episode 28: My Week!

1：我下课去找你啊！    我下了课以后去找你啊！
2：下课以后我去图书馆。   下了课以后我去图书馆。
3：她结婚以后就不工作了。   她结了婚以后就不工作了。
4：我知道她不喜欢我。    我已经知道了，她不喜欢我。
口语中可不用“了”，因为句中有“以后”表状态完成。如果要表示强调，要加“了”。

喵喵说汉语---HSK 4

“了”可用可不用的情况

A View from the Window (with transcript)

https://drive.google.com/file/d/1IRS00fusEOnIBYjoCLz0f16Oi6zCl9Oc/view?usp=drivesdk