$\text{1.}$ We have decorated the Chritmas tree a week ago.

The Chritmas tree has been decorated a week ago.

$\text{2.}$ I haven't met my old teacher for 2 years.

$\text{3.}$ The heavy language prevented the boy from carrying it.

Because the language was heavy, the boy couldn't carry it.

$\text{4.}$ They were such strong enough to lift the rock.

$\text{5.}$ My brother is a better badminton player than me.

My brother plays tennis better than me.

$\text{6.}$ My suit need cleaning by me before going to the party.

$\text{7.}$ No sooner had my father come home than we prepared the dinner.

$\text{8.}$ How long is it since they bought their house?

$\text{9.}$ He was made study harder by his parents.

$\text{10.}$ We didn't arrive early enough to see the first film.

$\text{11.}$ He apologised for eating his sister's cake.

$\text{12.}$ Facing a lot of people is the reason why he's always nervous.

$\text{13.}$ He was thought that waiting for the mess.

$\text{14.}$ We are excited about passing the final exam.

$\text{15.}$ We'd rather not tell him the news.