In my leisure time I like swimming, reading, and watching.
If you are contrasting doing an activity with simply watching then you don’t need to mention the activity:
||Do you do any sport?
||I like to watch.
(= I prefer watching than playing!)
Meanwhile if someone is showing you how to do something, you don’t need to mention the thing that they’re showing you:
||OK, now watch carefully!
However, if the thing you’re watching is something specific, then you need to mention that thing:
- In my leisure time I love to swim and watch movies.
- I don’t watch much TV now that we have YouTube.
This is especially important if the thing you are watching is TV or a movie, because watch collocates very strongly with these nouns.
Indonesians translating ‘nonton‘ need to remember that if you don’t tell your listener what it is that you’re watching, then as far as your listener is concerned, you could by watching almost anything, like watching paint dry or watching grass grow!
In my spare time I usually go out with my friends.
This is grammatically correct. However, if you’re talking about something you do regularly or habitually then present simple tense is all you need:
- In my spare time I go out with my friends.
Indonesians will feel a need to translate ‘biasanya’, but in English present simple tense already carries the meaning of usually, and so usually is redundant in a sentence like this.
Only use usually when you want to make a contrast between something you do habitually, and something that you do, or have to do, because of exceptional or unforeseen circumstances:
- In my spare time I usually go out with my friends, but today I have my IELTS interview.
At the weekend I like to spend my time to cook.
There are two problems here. First of all you are unlikely to spend anybody else’s time other than your own, so ‘my’ is redundant. Secondly, ‘spend time’ is much more commonly followed by _ing (gerund):
- At the weekend I like to spend time cooking.
You can also use a preposition phrase to show where you spend time:
- At the weekend I like to spend time in the kitchen.
And you can even combine these two examples:
- At the weekend I like to spend time in the kitchen cooking.
Now spend some time practicing ‘spend time’!