Excellent!  My comments below are simply ways to make these sentences sound more natural, but they are completely correct otherwise!

5 sentences

1) Talking to Japanese classmates everyday has helped me to become a fluent speaker.
2) Doing three jobs at the same time enables allows him to earn enough money for the down payment of for the house.
3) Doing aerobics keeps him fit.
4) Reading English newspapers regularly improves his reading speed.
5) Going to bars often may not help you to find a good boyfriend.

5 sentences

1) Talking to Japanese classmates everyday has helped him/her/me to become a fluent speaker.
2) Doing three jobs at the same time enables him to earn enough money for the downpayment/down-payment (we tend to combine these compound words into one) of on the house.
3) Doing aerobics keeps him fit.
4) Reading English newspapers regularly(,?) improves his reading speed.
5) Going to bars often(,?) may not help you to find a good boyfriend.

Note the two words in red ... it is not immediately obvious which verb they attach to - reading regularly or regularly improves, going often or often help. Just drawing it to your attention, there are potential ambiguities in English! A comma would resolve that, but I am not sure that is correct here.