1. Use the right form of the verbs in brackets 1. This man (know) from his experience what it (mean)....

Sure, here is the text with the verbs in their correct forms:

1. This man knows from his experience what it means.
2. Nothing happens by accident.
3. As a man grows older, he tends to be more skeptical.
4. My mother often tells me that you do not leave your problems behind you when you go to another place. Pain and heartache travel well. And indeed they do.
5. Mrs. Osborne owns this business and she runs it herself.
6. He is a complete mystery to me.
7. What does he do for a living?
8. In Rome, every building tells its own story.
9. When the weather heats up and you need to cool down, a lake, a river, a pool − is what your body and soul need.
10. My great-grandmother is very old, but she hears, sees, and understands everything quite well.
11. I remember that Margaret owns a villa on the Adriatic.
12. "The Bible says that the heart of man is exceedingly wicked," the Pastor replied.

Here's a brief explanation of the chosen verb forms:

1. Knows/means: Present simple tense is used for general truths and facts.
2. Happens: Present simple for statements of general truth.
3. Grows/tends: Present simple to describe habits or tendencies.
4. Tells/do not leave/go/travel/do: Present simple for habitual actions and general truths.
5. Owns/runs: Present simple for current ownership and actions.
6. Is: Present simple for a state of being.
7. Does.do: Present simple question form for occupation.
8. Tells: Present simple for a general truth about buildings in Rome.
9. Heats/need/need: Present simple for conditions and needs.
10. Hears, sees, and understands: Present simple for abilities.
11. Remember/owns: Present simple for memory and ownership.
12. Says: Present simple for citing written texts.

The present simple tense is often used in English to describe general truths, habitual actions, and states of being, which is why it's predominantly used in these sentences.

1. knows, means
2. happens
3. grows, tends
4. tells, leave, go, travel, do
5. owns, runs
6. is
7. does
8. tells
9. heats, need, need
10. hears, sees, understands
11. remember, owns
12. says

1. This man knows from his experience what it means.
2. Nothing happens by accident.
3. As man grows older, he tends to be more skeptical.
4. My mother often tells me that you should not leave your problems behind you when you go to another place. Pain and heartache travel well. And indeed they do.
5. Mrs. Osborne owns this business and she runs it herself.
6. He is a complete mystery to me.
7. What does he do for a living?
8. In Rome, every building tells its own story.
9. When the weather heats up and you need to cool down, a lake, a river, a pool - is what your body and soul need.
10. My great-grandmother is very old, but she hears, sees, and understands everything quite well.
11. I remember that Margaret owns a villa on the Adriatic.
12. "The Bible says that the heart of man is exceedingly wicked," the Pastor replied.