I have this problem where I can't retain a girl. 90% of them I get just the first date and never see them again. I thought it had to do with where I met them (mainly Tinder), so I manned up and
In this year I've been focusing more on meeting girls in real life (I've approached like 10, got like 8 instagrams and got 3 dates probably one more to come), but the problem maintains.

For example the situation with the girl I had recently:
Im Portuguese, and I was at the beach alone and a group of spanish girls came nearby,
(they are here studying for a few months) and basically I went there made a few jokes and got the instagram of one of them,
we spoke for a week and I got a date with her yesterday. I picked her up with my car in her university residence,
We went out for a drink and it was great she was showing signs of high attraction and I kissed her. After a while she kissed me,
we went back to my car and we started making out, I could tell she was super horny and so I asked if she could bring people to the residence,
she said no, and then after a while of making out I tolded her "lets go to the back of the car" but she said she wasn't going to do anything.
I tried like once more but that was it and I brought her home. I texted her a few hours after with a joke we had on our date and she didn't respond. Im 21 and she is 18 for reference.
What mistake you think I made?
At least I got to practice my spanish lol..

This type of situation has happened with dozens of girls in my life. In fact, I keep a list of the girls I had dates or situations with and they all ended in a similar way and its around 40 girls. I've been actively in the dating scene for like 1y and a half.
Im 179cm (5'10 / 5'11) , I work as software engineer from home, but I don't make enough money to move out of my parents house anytime soon which makes me have to go through these types of situations with girls in the car.
Maybe Im not escalating correctly in the car, what is the best way?
Should I aim to get dates without having sex? How would you approach dates if you were me?
I saw a video of Alex saying you should always try to have sex first date. However I don't know if this applies if you don't own your own apartment (like me), and for what Alex says, I can tell this is a situation of point of no return.

I also understand that this is a first world problem but I'm getting kind of tired of having so MANY temporary girls in my life and would like to keep one and get to know her for once. Maybe unrealistic in current society.

Thank you very much for the patience.