Speaking ‘No’ is not enough to decline a suggestion.
The good expression for this situation is だいじょうぶです which means 'I am fine'.
Speaking
Speaking 
Speaking Politics in Japan（日本の政治）
On this page, you can see the sample conversation script on the topic of Japanese politics.
Speaking Sentences to talk or write about manga
Manga, which was born in Japan is well known around the world. Let's learn how to talk or write about it in Japanese.
Speaking Tennis in Japan
On this page, you can see the sample conversation script on the topic of tennis in Japan.
Speaking Japanese castle（日本の城）
On this page, you can see the sample conversation script on the topic of Japanese castles.
Speaking Japanese speaking exam
The expressions below may be convenient if you have a speaking exam in Japanese.
Speaking 【Japanese daily conversation】Assorted
On this page, you can see basic questions with a sample answer which are useful for Japanese daily conversation.