Just two links to study Greek grammar
For those who want to start study modern Greek grammar there is a source I just noticed today: the relevant article of Wikipedia . There are a lot of examples there for the different parts of speech and a lot of tables for conjugation of nouns , verbs etc. This is not a complete Grammar of modern Greek of course , but it is a quite useful free content you can start with.
On the other hand , if you would like to check a Grammar in Greek language , there are also some options. The most classic modern grammar book that you can use is “Η ΝΕΟΕΛΛΗΝΙΚΗ ΓΡΑΜΜΑΤΙΚΗ ΤΟΥ ΜΑΝΩΛΗ ΤΡΙΑΝΤΑΦΥΛΛΙΔΗ” :
If you would like to download a .pdf file of that book press on that link.
These are just tips for those who are eager to study grammar. This is not the method that I propose actually , but some people like to study first and then to try to speak. This attitude is not the right to my opinion, but as long as I have some tips for my readers I will provide them.
On the other hand if there are any questions about Greek grammar or you need any explanations about how it works , just feel free to ask me in the comments …I will be glad to answer.