Beautiful - enjoyable friendly funny high interesting kind long narrow new short tall thin young
In Reading
1 Read the dialogue quickly and tick (V) the main thing
Nathan and Theo are talking about.
who their best friends are
who the people are in some photos
where they usually go on holiday
what they were like in the past​

All countries have conventional but important behaviour rules that could be explained by inhabitants only. So, you've come to Russia but you haven't know about these rules yet. I'll help you learn primary of them. 
Firstly,russuians usually cede pleces to aged people in the bus. We take care about our elderly. This rule should be known to you,for sure. 
Secondly,russians usualy take off their footwear before entering the house. Perhaps,it could seems rather strange. But this is russian behaviour rule.
Thirdly, we usualy say "enjoy your meals" to each other before dinner,supper. It's not typical for your country,isn't it? Also,when russians have a meet they can kiss each other. We don't open gifts out of hand,which was presented to us. There are many another rules. But, we have to remember foreigners don't aware about all our rules and as long as you staying friendly and polite don't worry about your a little bit strange behaviour.  
Вот исправленный вариант.

1. When I came home, my mom was cooking dinner for us. - Когда я пришёл домой, мама готовила обед для нас.
2. What are you talking about? — Nothing serious. О чём вы разговариваете? — Ни о чём серьёзном.
3. I am sorry I couldn't join you yesterday. I was preparing for my exam. - Извини, я не мог присоединиться к вам вчера. Я готовился к экзамену.
4. What did you say at a minute ago? — It was the funniest joke I've ever heard. - Что ты сказала минуту назад? — "Это была самая смешная шутка, какую я когда-либо слышала".
5. The spaceship captain noticed the satellite which was moving very fast. It was dangerous! - Капитан космического корабля заметил спутник, который двигался очень быстро.Это было очень опасно!