How to conjugated three verbs with and without que
In google translator, I typed in "I believe I can fly" and got "Creo que puedo volar".
I'm wondering what would happen if I didn't use the "que". Would it be "Creo poder volar" or "Creo poder a volar"?
Also I thought a conjugated verb followed by que would be followed by an infinitive like tener que. So shouldn't it be "Creo que poder a volar" or "Creo que poder volar". I'm not sure why I'm including "a", but it sounds right to me. However, volar already means to fly so adding "a" would mean "to to fly" (a volar). Why would tengo que volar be correct and not tengo que vuelo?
3 Answers
Hola Ramona,
Bienvenido al foro SpanishDict 
Aquí tienes algunos ejemplos que usan tres verbos con la palabra 'que':
1.Creo que puedo aprender a hablar español (indicative)
= I believe that I can learn to speak Spanish.
2.Quiero que aprendas a escuchar bien (subjunctive)
= I want you to learn to listen well. (literally: I want that you learn to listen well)
Other examples without the word que:
Quiero saber nadar = I want to know how to swim
Me habría gustado ir a visitar a mi abuela la semana pasada, pero estaba enferma
= I would have liked to have gone to visit my gramdmother last week, but she was ill.
You would say: Creo que puedo volar = I believe (that) I can fly. This is correct!
Your other examples are not correct. You need to use the relative pronoun, 'que'. In English we often omit the word 'that' as in your example: I believe (that) I can fly, but in Spanish the word que must be included in sentences like this!
You will learn with experience that the Spanish language is quite different from English and you cannot translate accurately between them using a literal, 'word for word' approach ...it just doesn't work! I know that from personal experience! 
Sometimes the translation machine can be accurate, usually when translating sentences that are literal ..they are not very accurate with idioms!
Tengo que volar is correct because this verbal construction: 'tener que' is always followed by a verb in the infinitive form! It would sound weird to my ears and horrible as an experienced Spanish speaker to hear somebody say: tengo que vuelo :(
I hope this helps
Corrijan mi español si es necesario, por favor
Simpler would be to say that one of the meanings of "que" is "that."
In English you can say I think that I can fly--or I think I can fly.---(no "that") In Spanish you have no choice. You must include the "that."
Creo que puedo volar. I think that I can fly.
This is not an answer, this is further questioning:
I want to explore the "Creo poder volar" aspect more.
In English I would normally say: I think (that) I can fly.
But I think I could say: I think myself able to fly. Not a common construction, but I think I have seen it.
Likewise in Spanish I would say "Creo que puedo volar". It would not have occurred to me to do otherwise, as that is how I always hear it.
But ones similar to original question can be found, and I would be interested in how these sound to native speakers.
http://www.spanishdict.com/translate/creer
creen haber descubierto el motivo they think (that) they've discovered the reason
http://spanish.about.com/od/infinitives/a/infinitives_after_verbs.htm
creer (to believe) — No creo estar exagerando. (I do not believe I am exaggerating.)
The one above by Gerald Erichson, who I have a lot of faith in.
