In particular, the labor theory of value, the tendency of the rate of profit to fall, overproduction and the self-defeating nature of capitalist competition? Like me explain...
The labor theory of value: Marx held that since all goods and services stem from a combination of labor and natural resources and since natural resources are given by nature, the value of goods and services stems from the labor employed in their production.
The tendency of the rate of profit to fall: Since capitalists are in competition for a limited market, they must produce as much as possible. This means that they must revolutionize the means of production in the form of new technology. Since the value of goods and services comes from the labor employed, this means that goods and services produced by the new machines will be sold for less than before and that combined by the cost of the machinery itself drives down the rate of profit.
Overproduction: Since revolutionizing the means of production is both necessary and drives down profit, such advances together with the context of competition for market share will from the standpoint of capitalist profit force the capitalist to overproduce.
The self-defeating nature of capitalist competition: Those capitalists who best maintain a balance between capturing market shares and avoiding overproduction attract more and more capital from investors. Those who do not go bankrupt and are then bought out by the more successful capitalists. This decreases the number of firms and transforms the surviving successful firms from proprietorships to corporations. This end of competition is thus caused by the previous existence of competition.