eijk1234. Difficult decision, difficult-ish questions.
"Is the contract solid?"
No. The contract varies by the time of day and in any case very few people feel it appropriate to look for what their contract entitles them to (read the thread on "Ryanair - a call to arms" to start to understand why).
"Will I really be flying 900 hrs and make the money they say?"
Yes to the 900 hrs. The money I can't advise about - it depends a bit on what "they" say!!
"Is it true that they intend is to change me to a permanent contract when available?"
Unlikely. They intend to do only what they find suitable to their needs (which might be to change you to a permanent contract when the time comes). Many contract pilots have long since met the legal requirements for full time employment entitlements, but have not chosen to assert their legal entitlements. Why? .... see "Ryanair - a call to arms" to get a sense of the environment.
"What about paying taxes and stuff, do I have to sort it out myself?"
Can't help you here. Ask your potential hiring company (and be careful with your questions and the answers to those questions ... it may be your last opportunity to ask questions for some time!!).
"Are things getting worse or better in Ryanair."
Worse. And heading downwards. But that does not mean that it is a bad decision for YOU to join Ryanair, just that it is a difficult decision.
The great debate at present is whether or not BALPA and IALPA can organise the Ryanair pilots to stop the rot. A lot will hang on the outcome. It is fair to say that, at the moment, there has never been such unhappiness and distrust of management. There are also pockets of happiness. But they tend to involve the new or innocent.