I believe future is for BTC and my investments will mostly on it. I wanna use Electrum as my main btc assets storing. As i heard exchanges is not safe for storing purposes.
Electrum is a good wallet. Just as others have said, you need to be careful when making use of online wallets to store large amounts of money. For example, if you want to start a weekly accumulation of $100 worth of BTC, it will be safe for you to use, but you should be very careful about the kind of links you visit online with the device on which you have that wallet installed.
And if you are to use mobile, it's not always advisable for you to carry about bitcoin holdings on your mobile device. Things happen now that only the ones we are willing to spend on a daily basis are expected to be kept on mobile wallets, which we move around with for security reasons.
While you think about the best hardware wallet to buy, try protecting the phrase of the electrum that you have chosen to use, and don't use any cloud storage as a means of protecting your phrase. The old, traditional means of saving phrases are the most recommended. (Paper and pen, and keeping the different locations that can only be accessed by you and those you share access with.)