Exercise

Today before the dinner, I felt led like having a like exercising. I got out on my bike and after about 15 minutes, I reached the foot <em>(more native.... I reached the bottom of...)</em>of a little mountain and I started jogging on the path up to the summit <em>(also, you could say "top of the mountain")</em> of the mountain after locking my bike. By the time I nearly get the summit,<em>(more native...)</em> As I approached the top it started raining and started to rain more and more.the rain became more and more big. I fastly runed to a big tree after I reached the summit. Once I reached the top, I found a tree and ran to it.  After a while when the rain started to stop <em>(or, when it was raining less,)</em> bacame little, I then started to go home.

American English Corrections

Exercise

Today, before the dinner, I felt like having a exercising so I went out on my bike ("To go out on" means to take your bike out of your basement or wherever you keep it and to then go on a bike ride. This makes perfect sense here. Of course, like Troy wrote, you can also say "I got on my bike" which means you sat on your bike, but I think you meant you went out for a ride on it instead which makes more sense with the sentence after it. I connected both sentences with "so" to make them relate to each other and for style reasons but leaving them as two separate sentences is fine too.) . After about 15 minutes, I reached the foot of a little mountain and I started jogging on the path up to the summit of the mountain (or "to the top of the mountain" or just "to the summit" to use fewer words and to avoid repetition of the word "mountain" in the sentence. Americans try to avoid repetition in writing.) after locking my bike. By the time I got to the summit (or "by the time I reached the summit"), it had started raining and the rain had begun to fall harder and harder (or "it had started pouring and the rain had begun to fall harder and harder" or "it started raining and the rain began to fall harder and harder" or "it started to pour and the rain began to fall harder and harder." Americans tend to use the simple past tense instead of the perfect tenses more.). I ran quickly to a big tree when I reached the summit. After a while, the rain (or "the downpour") lessened, and (then) I started to go home (or "and then I headed for home" or "and then I headed home." or "and then I made for home.").