Spanish language Q&A Forum

I guessed this correctly but when I clicked on the explanation of past participle examples in Spanish it did not explain why it is escrita? 

Can someone please explain?

Some examples use the verb “estar”.  But can we ever use “ser”?  Ex:  “Mis primos fueron aburridos hasta que viajaron a españa.”  Thanks.

To say I’m hiding 

It is estoy escondido and not estoy escondiendo 

Why not gerund ?

Would it be helpful to explain this way? 

sentado/a(s) = seated; tumbado/a(s) = laid?

The title of my question is only an example of several variations I've found on the same theme: when to use reflexive and when to use estar+participle? 

Me sorprendí cuando me propuso matrimonio

Estaba sorprendida cuando me propuso matrimonio

It seems to me that the reflexive above suggests more of an action (it surprised me...), while estar+participle suggests a state (being in a state of surprise).  

Could you explain and demonstrate by example how one might be chosen over the other?  

Also, the reflexive seems to be prompting me to add que+subjunctive (Me sorprendí que me propusiera matrimonio), but the participle version does not.

As you see, I'm a little confused and I wonder if my confusion comes from learning Latin American Spanish? The participle seems to occur more often when I read that variant. 

Saludos a todos

Please could you explain the following:

Los chicos estaban sentados en el borde de la piscina. correct
Los chicos estaban sentando en el borde de la piscina. not correct
The boys were sitting on the edge of the pool.

I am pretty sure that I have been taught to use the gerund rather than than the past participle in this kind of an example.

Many thanks  (Mainland Spain)

Would it be possible to use active participle? Are there cases in Spanish when both -ido/ado and -iendo/ando can be used and the meaning remains the same?