If an act which was started earlier and it still continues and it may continue in the future then you should use Present Perfect Continuous Tense.
Sub + has/have + been + verb + ing
If since/for came in a sentence apart from the above the situation then you should use Present Perfect Continuous Tense.
Eg:
- I have been working in this company for 3 years.
- She has been doing MBA since 2016.
- My sister has been preparing for LDC exam for 2 years.
- They have been building the bridge for several months.
- My uncle has been staying in Delhi since 2002.
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