Explanation usage of 得 and 地 Can someone explain me exactly when I have to use these two words? 
They are both pronunced "de", but I found some difficulties understanding why should I use 得 (or shouldn‘t) in some senteceses.

地 , to me, seems more like a word used to make another become an adverb, but I‘m not totally sure.
Chinese Grammar Info provides an excellent write up on the three distinct de particles. See the site for the full article.

The main points are:  

(的) de as the possessor or causing the possessive function:


  我的书
  
  wǒ de shū
  
  my book
  
  这是你的书。
  
  Zhè shì nǐ de shū.
  
  This is your book.


(地) de/di as the ly suffix


  慢慢地
  
  mànmande
  
  slowly
  
  他很快地吃饭。
  
  Tā hěn kuài de chīfàn.
  
  He eats quickly.


(得) de as a potential complement


  做得到
  
  zuò de dào
  
  can do
  
  我只有戴眼镜的话才看得清楚。
  
  Wǒ zhǐyǒu dài yǎnjìng dehuà cái kàn de qīngchu.
  
  I can only see clearly if I wear my glasses.


UPDATES (per request in comments):

More on 得. The article further states that this version of de relates to two types of complements: potential complements (which indicate that the attached verb has potential to have the action happen) and degree complements (speaks to the degree/amount that a potential verb may happen).

Potential complement


  听得懂
  
  tīng de dǒng
  
  can understand (from listening)


(and conversely)


  听不懂
  
  tīng bu dǒng
  
  can’t understand (from listening)


Degree Complement

Note the basic structure where the verb is followed by a description that includes the degree complements; very well, badly, very tall.

(basic structure)


  [verb] 得 [description]


(a few more samples)


  你说得非常好。
  
  Nǐ shuō de fēicháng hǎo.
  
  You said it very well.
  
  他做得不好。
  
  Tā zuò dé bu hǎo.
  
  He did it badly.
  
  她长得很高。
  
  Tā zhǎng de hěn gāo.
  
  She has grown very tall.


Beyond it's use as a particle, the article states:


  得 as dé When 得 is pronounced dé in second tone, it’s a verb meaning
  “to get” or “to acquire”.
  
  得 as děi When 得 is pronounced děi in third tone, it’s a modal verb
  meaning “must” or “have to”.