The main difference between since and for is that since is used with a particular point in time whereas for is used to specify the period of time.
For is used to talk about time amount or space. Time amount may be seconds, minute, hours, days, month and year. Time amount not need to be exact. To talk about vague time period for is used like for weekend, for years.
With a particular pint in time, since is used in English. Since use with present perfect and past perfect tenses. In many songs the word since use which you can hear on your mobile device or computer.
For use with a period of time while since used with a specific point in time. In similar verb tenses, for and since can be used. Here are examples:
I have been running for 7 hours.
I have been running for 5 pm.
We have studied here for 3 years.
We have studied here since 2017.