Considering the following:
I'm okay at listening and very well at reading, but not good at writing and speaking (input is open,output is closed) mainly because I've forgotten some Grammar and other things like prepositions, phrasal verbs etc. I know the words I need to make the sentence I want, but can't glue them together to make the sentence in right format or find which word is best for specific sentence. However, I understand and remember the format and its meaning when I see it. Also, English is considered "foreign language" here so it isn't spoken much except at English classes.
What are some effective techniques for someone in my situation to improve their ability to construct sentences? Are there any things I should avoid doing?
Should I keep saying and writing the wrong (maybe not) sentences?
Is there a good method to recover the things I know, but have forgotten?
Do I need teacher/tutor or are there some things I can do on my own with books/other things?
Should I start studying from the beginning as forgotten parts are spread across the learning courses?