Hi I got to some Ruins and I found that some of then have locked sections (Malada for a example)... what must I do to open those sections?

I have posted a topic on Ayleid ruins somewhere that might be useful to you. Seach under Varla Stones and you should find it. If sections of ruins are locked it generally means you need to be on a quest. The ruin of Malada is used on the first quest Umbacano gives you once you have collected three Ayleid statues and sold them to him. If you haven't found a statue yet look in the first ruin you see as you come out of the sewers. Sell it anywhere and shortly after the quest will start or take it straight to Umbacano.

One locked cave (Unmaked Cave I think) has a locked section but serves has no quest attached. There is no key. It is fixed by the unofficial oblivion patch.