If I sin and do something against the Torah does G-D really love me? Will I go to Gehenom?
G-d does love you, and he will always love you.
G-d chose every single Jew to be part of his nation. He chose both our souls and our physical bodies too. (To be precise, the soul is considered a child of Hashem and the body was chosen). Every Jew, no matter how much Torah or Mitzvos they observe, is dear to Hashem as an only child born to elderly parents.
Actually, you also love G-d at the very moment that you might be doing something that is against his desire, G-d forbid. This love is hidden in your heart, but can never be extinguished, and with just a bit of effort, it can easily be revealed.
Gehenom, like all punishments in the Torah, Toras Chesed (a Torah based on kindness), is primarily a purification process that souls go through to clean them from their wrongdoings. One who does Teshuva by regretting his passed improper deeds and deciding never again to return to them is forgiven by Hashem and can avoid this otherwise necessary mode of purification.
It is worthy to note that the proper path to take in serving G-d is to focus on fulfilling G-d’s desires for His sake, rather than basing it on how one will be rewarded or punished after their passing. At the same time, when it comes to preventing ourselves from wrongdoing we are to use any method at our disposal, even a method which is focused on reward and punishment. It is recommended to add to your study schedule some Chassidus, most significantly Chabad Chassidus where the concepts of Chassidus are brought across in a language one can understand, if you don’t learn this yet, where you will be able to learn how to serve G-d for His sake. In this generation, learning Chabad Chassidus is almost imperative for every single Jew.
Another point to remember is that G-d appreciates sincerity and effort, and has pleasure from even the small things we do. Every time we fight a war with our animal soul – even if we do not win the war, only fight – we make G-d happy and bring more holiness and blessing into the world.
May we merit to the coming of Moshiach, who is already on his way, when the entire world will reach the ultimate level of purification, and we will no longer need painful purification processes like Gehenom.
All the above is discussed at length in Chassidus, primarily in the book of Tanya, expounded upon in Likkutei Sichos and the Sifrei Hamaamorim.
Some pointers to explore:
G-d’s love and our love to Him: Tanya Part 1, Chapter 25 and 49
G-d’s pleasure from effort: Tanya Part 1, Chapter 27
Gehenom: Tanya Part 1, Chapter 7 and 8. Tanya, Part 3, Chapters 1 and 2.
Serving G-d for His sake: Rambam, Laws of Teshuva, Chapter 10.