Hi, i need to know guangzhou train/subway ticket price

It costs CNY8 in total.

1. if to choose taxi or train ware is better.
2. I want go to sunflower garden. in august is the right time or not and what line i need to take?

Well, by contrast, metro is the best way to go. If you go by taxi, the fare can be CNY110-120.

Generally, it is best to have fun the Sunflower Garden during May and Oct. so it is fine to go in Aug. Here is the general way for your reference:
take subway line 4 to Jiaomen Station and change to bus Nansha line 2 to get there.

sorry, how can i get train to shenzhen from my hotel grand continental apartment. it impossible if i go 1 day that mine take first train morning and come back the same day night.

You are suggested to take a high speed train from GZ Railway Station.
First, take metro line 6 at Beijing Rd, which is 100 meters east to your hotel, then transfer to line 2 at Haizhu Square, get off at GZ Station.
The train is available from 6:00 to 22:23. It takes about 1h 30 minutes and CNY79.5 for a second seat, CNY99.5 for a first one.
Of course you can back to GZ within a day. The last train departs at 20:40 from Shenzhen to GZ.

must i take Smart Card (called Yang Cheng Tong in Chinese) or not because i am in the city for 5 days

Well, you are suggested to buy one, since you will stay there for five days, and the card could be used in metros, buses and some convenience stores.
You can buy it in metro stations, notice you need to buy the Deposit cards, which can be refunded when you leave.