This is a very standard option agreement, nothing unusual here.
What exactly means: "strike price determined by the board of directors at the time of the Grant"?
If a company isn't publicly traded, the value of the company if often determined by the board of directors in regular interval. This is then used to set the current stock price which will be your strike price.
Do I need to ask to word it differenly?
You can ask but they won't change it. You can ask for the current price and when the next board of directors evaluation will be. Chances are, your strike price will be close to the current on. However, timing does matter here: While unusual it's not impossible that the Board makes a large evaluation change which can affect your strike price both ways
Do I need to say that after the cliff, they cannot remove the equity.
No. That's not how it works. First of all: you do NOT own equity until you decide to exercise the options and buy actual stock. The cliff means you are not allowed to exercise during the first year. Once options are vested, you can exercise whenever you want. That includes "not at all", most people will refrain from exercising until there is a way to sell the stock: either through a private investor/buyer or by going public.
What more can you tell me please? 🥺
Stock options are COMPLICATED. I strongly recommend you educate yourself about them. A good resource is https://www.amazon.com/Consider-Your-Options-Equity-Compensation/dp/1938797175/. Buy it and read it (or something similar).
While options can be a fantastic opportunity, there are considerable risks and pitfalls. Besides the mechanics of the options themselves, there are very complicated tax implications and at least in the US some people have been bankrupted by not managing this correctly.