are e-commerce transactions 100% safe??

It is pretty safe with all the encryption measurements, monitoring systems and national police of multiple countries as well as other governmental organizations who keep a close look on international online money flows. Just make sure you buy from webshops preferably using PayPal or your credit card. Credit cards give the best protection, if you check your transactions and see a transaction you're not familiar with you can call your credit card and say it's unauthorized and things like that. PayPal does give some buyer protection but only for physical goods and you need to store all evidence and even then PayPal might sometimes decide to not give you the benefit of the doubt. Make sure those webshops have hallmark or quality mark that shows they're registered with at least a national organization that guarantees your privacy.