The reasons for your refusal are pretty clearly laid out in the letter. Let's explain in more detail.
"The transfers are sporadic dating back to 2016" "Sporadic" means they happen infrequently and irregularly. If someone is supporting you financially, then they normally make regular payments to you, monthly or weekly. This is not what the officer is seeing, and it makes him believe that your brother is not actually giving you regular financial support. You need to explain why the payments are irregular. If you began being dependent on your brother in May, then there should be a distinct difference between payments before that and payments after that.
"There is other income in your bank account that does not appear to be from your sponsor." You say these are small amount you collect for a friend. If that is the case then you need to provide documents to prove that. Also if you collect them for a friend then you presumably pass them on to that friend after a bit, and you need to show the transactions in your bank accounts where you send the money to the friend. You call the amounts "small", but officers are rarely concerned with items that are "small" compared with your income. It is also unusual (and suspicious) for someone who is not financially independent to be processing transactions for other people.
"You have not provided evidence which fully details your circumstances." It looks as if the bank statements you provided either don't match up with your statements of income and expenditure, or don't show the normal transactions that might be expected with everyday living, leading the officer to believe you have economic activity that is not shown there. You absolutely need to provide more information.
"I think I never mention that I am unemployed" You should have clearly stated this in your application.
After two refusals it is very likely that you will attract another refusal unless your application is absolutely perfect and complete. Repeated applications are themselves suspicious, because it makes them think you have a different reason for wanting to come to the UK than a simple tourist visit with your brother. Perhaps you should consider visiting your brother in Finland rather than going with him to the UK? Hiring a UK lawyer may well be necessary, but will cost you more money than a tourist visit would justify.