Hi Helen,
"Spoken" is a past participle. You will use it with:
- the passive voice (the truth was spoken...)
- in perfect tenses (she has spoken English for 10 years / they had spoken English for 10 years but then...)
"Speaking" is either the gerund or the verb in continuous tenses:
- Gerund: I like speaking English
- Present continuous: I am speaking English right now
- Past continuous: I was speaking English yesterday when the phone rang
- Present perfect continuous: She has been speaking English for 10 years
To answer your question in your title, you have a few possibilities:
- Improve my spoken English
- Improve my English speaking skills
- I understand spoken English
Happy Friday!
Lou