A person who is a big fan of big pop star finds a cardboard poster of that celebrity takes a picture of himself with the cardboard. And says,
'Since chances of meeting my idol in this life are dim. This shall do; provide the satisfaction.'
It's bad writing, plain and simple.
I think the text is trying to say this:
Since chances of meeting my idol in this life are dim, I'll have to be satisfied with this.
However, there are serious punctuation problems in the original. First, this is not a complete sentence, so it shouldn't end with period:
Since chances of meeting my idol in this life are dim.
although it could be made a full sentence my taking out the first word:
Chances of meeting my idol in this life are dim.
Second, semicolons are used to separate complete sentences that are closely related in theme. As one writer's website explains:
Example: Tom earned his bachelor’s degree last summer; his sister earned hers in the fall.
These sentences are related thematically; both discuss academic degrees and when they were earned, so the semicolon is appropriate. Of course, a period would also be appropriate.
The three words:
This shall do.
is a complete sentence, albeit a brief one. So is:
Provide the satisfaction.
although, as a standalone sentence, it's a command to provide satisfaction. The way it is worded, this sentence has nothing to do with the selfie with the poster, even with the semicolon. Punctuation alone can't change the meaning of that sentence.
I can think of ways to use a semicolon correctly in this context, but I'm not going to provide it here, because it seems too likely that I'd be doing your homework for you.
The only context I can think of where what you've written would make any sense at all is where you've been given an exercise telling you to use a semicolon in sentence. (If I'm right about that, I don't mind telling you that you need to try again, but I'm not going to provide the answer outright. If that assumption is wrong, however, feel free to edit your question to provide more background information and context, and perhaps I'll edit my answer as well.)