Which term can be used to describe a person who usually does his works by his own, for example, repairs his car himself, learns through self-studying, etc. (I look for something more specific or specialized term than "independent")
One word : Autodidact : a self-taught person.
Auto- means "self" and "didact" comes from the Greek word for "teach.
If you're an autodidact you've done most of your learning on your own.
An amateur may have those skills:
- is generally considered a person attached to a particular pursuit, study, or science in a non-professional or unpaid manner. Amateurs often have little or no formal training in their pursuits, and many are autodidacts (self-taught).
In situations where teamwork is required (e.g. many software engineering firms), a positive term for someone who is able to work on their own when needed might be "self-starter" (a term which admittedly has become somewhat cliched in the corporate world). A person who is unable to work with others and solely works on their own might be referred to in a negative context as a "cowboy" or even a "loner", though the latter is rarely used, as it has connotations about the person's ability to interact socially that the former term does not.
Occasionally I have heard of "cowboy" being used for software engineers in a positive light, but much more frequently it is used in a derogatory fashion, implying the person is unwilling to work with others, follow rules or methodologies, or consider others' opinions or needs.
Merriam-Webster: cowboy 3. one having qualities (as recklessness, aggressiveness, or independence) popularly associated with cowboys
A jack-of-all-trades is someone who is capable of doing a wide variety of jobs or possesses a wide variety of skills. This phrase can be used positively, but it may have negative connotations as a longer version of the phrase is "Jack of all trades, master of none," implying that someone can do a little bit of many things without actually excelling at any of them. More positive terms are polymath and Renaissance man.