Is it safe to register in Snapdeal and Grabdeal and use creditcard to buy items online?

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Hi,

So while using facebook, I clicked on ads abt. discount on mobile on right side and pages like snapdeal and grabdeal opened. To access to it I have to register or sign in. Before registering to it I want to get some genuine advice, whether it is safe to register in this website. I mean if I register and provide my e-mail id and phone number are there chances I would get unnecessary marketing e-mails and phone calls. Also after registering I will have to use credit card or debit card to buy any items online, so is it safe to use credit card or debit card there? Are this website fake & cheater or it is safe to use? If we buy or order any item online there do we actually receive it to our home or chances are there to lose money. Can they lick our card number. phone number and email id and can it be misused. Please give me your valuable, true and genuine suggestion and share your experience of using this websites if you have any...Thank you.