Stocks vs bonds: what's safer to invest in?

Stocks and bonds both have risks, they are just different risks. That being said, 20 years is quite a while in the investment world, so you need to have a well diversified portfolio that includes both stocks and bonds. The question is in what ratio, and that can only be answered by a planner who can sit down with you and assess your overall financial situation, your goals, your risk tolerance, etc.
Given that you say you have little saved thus far, while 20 years is a long time, it isn't as long as would be ideal, so you will probably need to take a fair amount of risk coupled with increasing your savings as much as possible. Basically, you will want to try to "make up for lost time" by trying to gain higher returns than being very conservatively invested as well as put as much away as possible.
I would suggest talking with a fee-only planner who can look at your complete financial picture and suggest what approach would best serve you. Most fee-only planners charge between $175 and $300 an hour, but it could be money well spent if it will help get you on a path to a quality retirement 20 years from now.