I'm a smartphone addict.
我是经常玩手机。
Be addicted to.....“对...上瘾”
Are you or your teen addicted to your cellphone?
你或你的孩子经常玩手机么？
Phone addiction is a common thing these days.
手机上瘾是现在很常见的一件事。
2. obsess 相关表达
be obsessed with sth “对...着迷”
We should not be obsessed with smartphone all day.
我们不能整天沉溺于手机。
3. Overuse
over 多加在动词或名词之前，构成包含“过度；过分”之意的新动词或名词:
overstudy n.用功过度(over+study学习)
overwork n.过度劳累(over+work工作)
overact v.表演过火(over+act演出)
Parents should help their kids to avoid overusing cell phone or social websites in general.
父母应该帮助孩子避免过度使用手机和一般社交网站。
4.spend time on/ doing sth... 花费时间在某事上
Nowadays, many people spend much time on smartphone.
现在许多人玩手机度日。
The average smartphone owner spends over two hours each day on the device.
人们每天会花超过2个小时玩手机。