How to create a storyline?

It sounds like you're struggling with both cliches and structure.

For cliches, here's one solution. Start with your basic situation between these two characters. Maybe they've just met, or are falling in love, or are already in love. Now make the worst possible thing happen to one of them. Not just the worst in regard to the love story, the worst, period. How does the character handle it? How about their lover?

On structure, I usually plan novels with a spreadsheet. Columns are characters and anything else I need to keep track of, from seasons and weather to how much money somebody's got to how long until her ex gets out of jail or the army or how sick his dad is. Rows are for plotting, starting with basic structural elements.

The Hook: sentence, paragraph, or page which draws the reader in
Stage One: setup showing how things are for main character (0-10%)
First Turning Point 1: the opportunity for change (at 10%) (<--something awful happens!)
Stage Two: the new situation and what it brings (10-25%)
Second Turning Point: the change of plans possible because of new situation (at 25%)
Stage Three: progress toward the new goal (25-50%)
Third Turning Point: the point of no return when character commits irrevocably (50%)
Stage Four: complications and higher stakes (50-75%)
Fourth Turning Point: the major setback (75%)
Stage Five: the final push (75-90/99%)
Final Turning Point: the climax (90 – 99%)
Wrap It Up: the aftermath

When my plan is done well, I see significant development in any column or row picked at random. Of course some columns get silly ("Still dead.") but this works well for me.

There's no one right way to plan, of course, but give this a shot and see if it works for you, too.