I have a large amount of money in a lot of small coins in my wallet (most of them like 0.0002 BTC).
But whatever I do, I loose about 15% due to transaction fees, because transactions are too large.
Is there any tool for optimization of transactions, which could combine those coins into transactions with minimal or zero fee?
If the coins are in the same wallet then you should be able to send your “large amount of money” in one transaction.
If your coins are spread across multiple wallets in the same client then you would need to take the 15% loss. Or not pay a transaction fee and hope your coins get validated by a very friendly miner. (I would advise the former.)
In the event that your coins are spread across multiple wallets, you should bite the bullet and send them all to a single wallet so you don’t continue losing money in the future.
It also might be a good idea to have slightly larger transactions, so you don’t pay as many fees.