A short sentence training

Do you wan to go out tonight ?
Est-ce que tu veux sortir ce soir ?

Can you bring your friends, please ?
Este-ce Est-ce que tu peux amener tes amis, s'il tu te plaît ?

Does he want to go swimming with us ?
Veut-il aller à la piscine avec nous ?

They can't start a car (in sense they are unsucesfully trying ...)
Ils ne pouvent (?) peuvent pas démarrer une voiture.

I want to meet your brother or your sister.
Je veux recontrer ton frère ou ta soeur.

Why do you always say that ?
Purquoi toujours tu dis cet ? Pourquoi tu dis toujours ça?
 

I have to clean the car.
Je deux propre la voiature dois nettoyer la voiture

I can't tell you that
Je ne peux pas dire cet ça

You have to become the best engineer in the country !
Tu dois devenir le meilleur ingenieur à le du pays !

Merci et bonne journée !!!

A short sentence training

Do you want to go out tonight ?
Est-ce que tu veux sortir ce soir ?

Can you bring your friends, please ?
Este-ce que tu peux amener tes amis, s'il tu te plaît ?

<em> Pozor</em> : "ty" in accusative pád is "te" in French. "tu" is only for pronoun-subject.

Does he want to go swimming with us ?
Veut-il aller à la piscine avec nous ?

They can't start a car (in sense they are unsucesfully trying ...)
Ils ne pouvent (peuvent) pas démarrer une voiture.

<em>Pozor</em> : Actually, you already did good job because your sentence is well-built. Your mistake is a misunderstood between two sounds which are /œ/ like "soeur" and /u/ like "pou". This mistake can be made when your ear isn't trained enough when you have to translate sounds from a speech.

I want to meet your brother or your sister.
Je veux rencontrer ton frère ou ta soeur.

Why do you always say that ?
Pourquoi dis-tu toujours cet ça/cela?
<em>Pozor</em> : Generally, in informal way, you can put in interrogative form the subject before verb. But, in formal one, it's better to reverse that form. Adverbs are generally put after verbs. In French, "tenhle" in 4. pád is "cela" in formal and "ça" in informal way. "cet" is only as demonstrative pronoun in 1. pád.

I have to clean the car.
Je dois deux nettoyer propre la voiature.

<em>Pozor</em> : let's analyse that sentence. Because your second sentence with "to have to" is correct, I think you forgot to put the right word and mistranslated the word "to" into "two". "Propre" is inappropriate because is an adjective. "Propre" is literally "to be clean". "Nettoyer" is the right word for the action "to clean sth". The mistake is made due to your wrong listening of "voiture" and your confusing writing . You listen [vouature], so I think you thought to get the right sound [voua] you needed to add genuinely an "a" after "i". Despite, /w/ is a semi-vowel which can be written as [oui], [oy] ou [oi].

I can't tell you that
Je ne peux pas vous dire cela

You have to become the best engineer in the country !
Tu dois devenir le meilleur ingénieur du pays !

<em>Pozor</em> : Take care about accents in French. It's as important as háček, čárka and kroužek in Czech. About partitive, let's have a glance at that italki link by that great French teacher :

http://www.italki.com/article/592/your-guide-to-partitive-articles-and-prepositions-in-french

Merci et bonne journée !!!

J'espère que cette correction t'a été utile pour améliorer ta compréhension du français.

Nashle!