Here are the correct forms of the verbs in each sentence:

1. If you **come** into my garden, my dog will bite you.
2. If I **learned** Russian, I could read your books.
3. If it is sunny, I **will go** fishing.
4. If I **were** a bird, I could fly everywhere.
5. He can get a good job if he **has** an English certificate.
6. If I had enough money now, I **would buy** that car.
7. If he **has** free time, he'll play tennis.
8. Unless we start at once, we **will be** late for school.
9. If she invited me to the party, I **would prepare** a cute present for her.
10. Unless you study hard, you **will not pass** the exams.
11. If the weather **gets** worse, the flight may be delayed.
12. They **would sell** their old house if they could find another cheap large one.
13. Unless he told me the truth, I **would not help** him solve the problem.
14. John can’t pass the exam if he **does not practise** harder.
15. If she flies to Da Nang next week, she **will phone** you.
16. If she needs a computer, her brother **will give** her his computer.
17. If we had a yacht, we **would sail** the seven seas.
18. My brother would buy a sports car if he **had** enough money.
19. If we **win** the lottery, we would travel around the world.
20. If you have free time this afternoon, **will we meet** at the club?

Feel free to ask if you need further assistance!