Is possible to read somewhere how much can I deduct from taxes for using phone, internet, gas, office supplies, etc.

A simple Yahoo or Google web search will give you dozens of sites, including the IRS publicaton.

They have all of them blocked for me here in China (welcome to monitored internet) but it is easy to find.

Next are they just for business, you can not use your personal cell phone for business and deduct it, you have to have a business phone, and normally a personal phone, That is the reason you see so many people with two cell phones,
Same with other costs, are they just for your business or are they personal bills and personal use that you sometimes use for busienss

I agree with Fr Chuck.

If you are looking for business deductions, your best bet is to get professional tax help.