Have half of BTC at hand. Want to find a way for better investment rotation to be done. So far invented such a scheme. The whole amount to be exchanged for any local currency.
What is a better investment if not bitcoin? You would not make any profit with any currency. Or have you given up on bitcoin and think that you have reached the peak of bitcoin? Personally, I would just keep on holding bitcoin but if you want to invest in something else with your bitcoin well that will depend on how much you have. You can get into real estate. Or any business.
Second: How to make sure I use "clean" BTC from source of exchange?
First of all, bitcoins are bitcoins. They are neither clean or dirty. They just exist as it is but if you really are keen on using only "clean" bitcoins then if you are using exchanges then I think you are pretty safe. If you really want to make sure then you can of course follow a trail. All bitcoin transactions are recorded you just have to follow it to see the source.