Hi and welcome!
Run your recipe through a
lye calculator like
www.soapcalc.net to make sure your lye amount is correct. It defaults to 38% water WRT oil weight and 5% superfat which are appropriate for new soapers. Do this for ANY recipe you find, in a book or on the internet. There is a lot of misinformation out there and it would be a shame to have lye-heavy soap the first time around.
Sunflower oil can have a short shelf life and can lead potentially to rancid soaps. There are two kinds - one is high oleic and if you look at the label on your oil, if it's higher in monounsaturated fats then it's the high oleic kind. The regular kind is high in linoleic acids which is more prone to spoilage. Generally, sunflower oil is best used in lower quantities - say 20% of your recipe.
You might want to consider using olive oil instead of sunflower - where I live there isn't much difference in price. Regular olive oil (not virgin or extra virgin) is fine and even preferable in soap. You could also try pomace olive oil which is cheaper still. Some soapers find that it speeds up trace but that hasn't been my experience.
Finally, your recipe calls for fragrance at 1% of your oil weight. That's likely to be pretty faint in the final product. Lemongrass is pretty potent and it sticks well. You might want to up your ratio to 30 grams or 3%.
I think CP is easier than HP but everybody has their own opinion on that.
Finally, a good site for beginners is
www.millersoap.com Her recipes are large so they'd need to be scaled down and run through a
lye calculator as you would do with any recipe. There is a lot of helpful information there.
Good luck - hope this isn't overwhelming!